California Arrears Interest 2026: How the 10% Rate Is Calculated

California Child Support Arrears: The 10% Interest Rate Explained

California ties child support arrears interest directly to the statutory judgment interest rate. Cal. Fam. Code § 17433.5 provides that interest on unpaid child support accrues at 10% per year — the same rate courts apply to money judgments under CCP § 685.010. That statutory alignment matters: when people ask whether child support arrears "grow like a credit card" or "grow like a court judgment," the answer in California is the latter. The rate is fixed by statute, not negotiated case by case, and it has been stable at 10% for planning purposes across the years most families are dealing with back support.

Why 10% is significant in real dollars. Ten percent sounds modest until you multiply it across years of missed payments and multiple monthly installments. A single $1,000 payment that remains unpaid for three full years generates $300 in interest under simple interest math ($1,000 × 10% × 3 = $300). That is not compounded growth — year two does not charge 10% on $1,100 — but it is still $300 on top of the $1,000 principal for one missed month. Scale that across a year of missed $1,000 payments, each running its own clock, and the interest column becomes its own substantial debt.

The rate applies to child support principal that was due and unpaid. It does not rewrite the underlying order. If a court ordered $1,200 per month and the paying parent paid $800 for six months, the unpaid $400 per month for those six months becomes arrears — and each $400 slice begins accruing interest from its original due date under § 17433.5, not from the date someone finally noticed the shortfall on a statement.

Judgment interest vs. child support interest — same number, different context. CCP § 685.010 is the general California judgment interest statute. Family Code § 17433.5 specifically addresses child support. Using the same 10% rate avoids forum-shopping arguments about whether back support should grow faster or slower than other court-ordered debts. For custodial parents, that means the law contemplates meaningful compensation for delayed payment. For paying parents, it means delay is expensive in a predictable, statutory way — which is exactly why payment plans, modifications, and early settlement conversations matter before balances snowball.

What the 10% rate does not do by itself. Statutory interest does not automatically mean every account statement you receive already includes interest. In some pathways — especially informal arrangements or cases where no one has requested an interest determination — the balance may show principal arrears only until a court or agency adjudicates interest. The 10% rate is the law's measure once interest applies; getting interest onto the enforceable balance often still requires procedural steps discussed later in this guide.

California's 10% sits in the middle of the national picture. Some states charge no statutory interest on child support arrears unless a court orders it. Others run higher effective rates or compound in practice through fee structures. California's approach is straightforward: simple interest, 10% per year, from each payment's due date. That simplicity is deceptive only because the "each payment" rule makes the arithmetic multi-layered even though the rate itself is flat.

If you are trying to estimate what back support might cost in your case, start with the statutory rate and the due-date rule, not with a single balance times years. TheLegalCalc's California child support arrears interest calculator at /child-support-arrears-interest-calculator/california is built for that payment-by-payment logic. For the statutory text itself, the official California Legislative Information site at https://leginfo.legislature.ca.gov publishes Family Code § 17433.5 and CCP § 685.010 in full.

Simple Interest, Not Compound: What This Means in Practice

Simple interest means the interest charge each year is calculated only on the original unpaid principal for that payment — never on prior interest that has already accrued. California child support arrears under Cal. Fam. Code § 17433.5 follow that simple model. The same 10% annual rate from CCP § 685.010 applies every year to the same overdue base amount until that specific installment is paid off.

The contrast with compound interest is easier to see with numbers than with definitions. Suppose a parent missed a $1,000 support payment due in January 2024 and paid nothing toward that specific installment for three years. Under simple interest at 10% per year, the interest after three years is $1,000 × 10% × 3 = $300. Total owed for that installment: $1,300. Under compound interest at 10% annually, year one adds $100 (10% of $1,000), year two adds $110 (10% of $1,100), and year three adds $121 (10% of $1,210), totaling $331 in interest — not $300. California's statute produces the $300 result, not the $331 compound result.

That $31 difference on one missed payment grows with time and with more missed payments. Compound interest punishes long delays exponentially. Simple interest punishes long delays linearly — still seriously, but predictably. For a paying parent trying to prioritize which arrears to attack first, simple interest means you can calculate the cost of delay without recursive math. For a custodial parent owed back support, it means the statutory interest is substantial but not the runaway compounding associated with some consumer debts.

Each missed monthly payment is its own simple-interest stream. If a parent missed $1,000 every month for twelve months, you do not calculate 10% on $12,000 times one year and call it done. You calculate twelve separate simple-interest streams, each starting on its own due date. The January missed payment accrues $100 per full year. The February missed payment accrues $100 per full year but starts one month later, so at any snapshot date it will always be one month "younger" than January's stream. By December, the December missed payment has barely begun accruing while January's has nearly a full year of interest.

Partial payments change the principal base for that installment, not the interest formula. If a parent owed $1,000 for January 2024 and later paid $400 specifically applied to that month, the simple-interest base for the remaining January arrears becomes $600. Interest continues at 10% per year on the $600 unpaid residue from the original due date — subject to how the Local Child Support Agency (LCSA) or court applies payments, which generally follows priority rules for current support, arrears, and interest.

Why "simple" still feels complicated in real cases. Human beings want one number on a statement: "You owe $X." California law wants fidelity to each due date. Software, LCSA accounting systems, and good calculators exist precisely because simple interest on forty-eight missed monthly payments is tedious by hand. The legal model is simple; the bookkeeping is not.

When people compare California to credit cards or payday loans, the important takeaway is rate plus structure. A 10% simple statutory rate is lower than many consumer APRs, but it applies to support principal that courts and agencies enforce aggressively — wage withholding, tax intercepts, license suspension, and passport denial do not require compound interest to be life-altering. Simple interest is not "soft" interest when the principal is large and enforcement is active.

Use the simple-interest formula as a sanity check: Interest = Principal × 0.10 × Years. Convert partial years to decimals where needed (for example, 14 months ≈ 1.17 years). If your estimate assumes interest-on-interest, you are not modeling California law correctly.

How Each Payment Gets Its Own Start Date Under § 17433.5

Cal. Fam. Code § 17433.5 is explicit that interest on unpaid child support runs from the date each payment was due. That single statutory phrase — "each payment" — is the core reason California arrears interest calculations differ from the back-of-the-envelope method many parents try first: total balance × 10% × years.

The due date is the trigger, not the discovery date. If support was due on the first of each month under a court order, a missed March 1, 2024 payment begins accruing interest on March 1, 2024 — even if nobody updated an online portal until August, even if the parties were informally arguing about custody, and even if a formal arrears judgment was not entered until later. Waiting for "official" recognition does not rewind the clock backward in the paying parent's favor.

Example — two payments, two clocks. Imagine $500 due January 1, 2024 and $500 due February 1, 2024, both unpaid through January 1, 2026. The January payment has been overdue for two full years: $500 × 10% × 2 = $100 in interest. The February payment has been overdue for one year and eleven months — call it 1.92 years for planning: $500 × 10% × 1.92 ≈ $96. Total interest ≈ $196, not $1,000 × 10% × 2 = $200 as if the balance were one lump sum with one start date. The difference widens as the gap between oldest and newest missed payments grows.

Example — $1,000 monthly misses for a full calendar year. Twelve $1,000 payments missed from January through December 2024, calculated as of January 1, 2026: the January 2024 miss has two years of interest ($200), February 2024 has 23 months ($191.67), March 2024 has 22 months, and so on down to December 2024 with 13 months ($108.33). Summing those separate streams yields roughly $1,308 in total interest on $12,000 of principal — materially different from treating $12,000 as one two-year-old lump ($2,400 interest) or as one one-year-old lump ($1,200 interest).

Example — longer horizon. A $1,000 payment due June 1, 2023, still unpaid through August 1, 2026, has been overdue about three years and two months (roughly 3.17 years). Simple interest: $1,000 × 10% × 3.17 ≈ $317. That figure is a planning estimate; exact LCSA accounting may use month-by-month allocation rather than decimal years, but the scale is what matters for negotiation.

Current support vs. arrears timing. When a parent is behind but still accruing new monthly obligations, each new month adds another principal slice with its own due date and its own interest start. The account is a stack of timers, not a single melting ice cube. Paying "something" each month may cover current support without touching oldest arrears — leaving the longest-running interest clocks still spinning.

Informal agreements do not pause statutory clocks. Parents sometimes agree verbally to "skip a few months" or "pay when bonus season hits." Unless a court order modifies the obligation, the due dates in the order still control interest accrual under § 17433.5. That is one reason documented modifications matter more than hallway promises.

Judgment entry vs. per-payment accrual. Entering arrears as a judgment can unlock additional enforcement tools, but it does not replace the Family Code's per-payment interest framework for support that was due before judgment. Think of judgment status as enforcement packaging, not as the birth date of interest.

Practical record-keeping for custodial parents. Maintain a payment ledger keyed to order due dates: amount due, amount paid, date paid, shortfall. That ledger becomes the backbone of any interest request. For paying parents, the same ledger is how you disprove overstated balances or show which months were actually satisfied.

The payment-by-payment rule is why generic debt calculators fail for California child support. You need a tool or spreadsheet that lists installments, not just a principal total. TheLegalCalc's California arrears interest calculator at /child-support-arrears-interest-calculator/california follows that installment logic.

Step-by-Step: Calculating California Arrears Interest

Calculating California child support arrears interest by hand is tedious but conceptually linear if you respect Cal. Fam. Code § 17433.5 and the 10% simple rate tied to CCP § 685.010. Follow these steps for a planning estimate before you rely on an LCSA statement or court order.

Step 1 — Gather the order and payment history. You need the monthly (or weekly) support amount, the due date rule in the order, and a chronological list of what was paid and when. Use official LCSA or State Disbursement Unit records when possible — not memory. Cash payments without documentation often disappear in disputes.

Step 2 — Build an arrears schedule by due date. For each due date from the first missed payment through the present, record: (a) amount due, (b) amount paid applied to that installment, (c) unpaid principal remaining for that installment. Each row is a separate interest stream.

Step 3 — Compute elapsed time from each due date to your calculation date. Express time in years or months consistently. Many planners use years as decimals: months ÷ 12. Example: 26 months = 2.17 years.

Step 4 — Apply simple interest per row. Formula: Interest = Unpaid Principal × 0.10 × Years. Do not add interest from one row into the principal of another row. Do not compound.

Step 5 — Sum principal and interest. Total arrears = sum of unpaid principals across all rows. Total interest = sum of interest across all rows. Total balance = principal + interest (subject to any payments specifically applied to interest).

Worked example A — single missed payment. $500 due January 1, 2024. Nothing paid through January 1, 2026. Elapsed: 2 years. Interest = $500 × 10% × 2 = $100. Total for that installment: $600.

Worked example B — longer single stream. $1,000 due June 1, 2023. Nothing paid through August 1, 2026. Elapsed ≈ 3 years 2 months (3.17 years). Interest ≈ $1,000 × 10% × 3.17 = $317. Total ≈ $1,317.

Worked example C — twelve monthly misses. $1,000 due on the first of each month, January through December 2024, unpaid through January 1, 2026. Calculate each month separately, then add. January 2024 row: $200 interest. February 2024: $191.67. Continue through December 2024: $108.33. Combined interest ≈ $1,308 on $12,000 principal — illustrating why lump-sum shortcuts fail.

Step 6 — Adjust for partial payments and allocation order. Real cases rarely leave entire years wholly unpaid. When a $600 payment arrives, agencies typically apply it according to priority rules — often current support first, then arrears principal, then interest — but orders and agency policy matter. A partial application reduces the principal on specific installments and therefore reduces future simple interest on those installments only.

Step 7 — Compare your estimate to official balances. LCSA systems may round differently, include fees or costs separately, or reflect interest adjudication dates you did not know about. Treat your calculation as a planning estimate, not a binding figure.

Step 8 — Model payoff strategies. Because oldest installments have the longest clocks, lump-sum paydowns that retire the earliest missed months first stop the most expensive interest accrual. Paying only current support while ignoring oldest arrears leaves the highest-interest slices untouched.

Common errors to avoid: using the date arrears were "noticed" instead of the due date; compounding annually; multiplying one total principal by one average years figure; ignoring partial payments; mixing pre-modification and post-modification amounts without splitting rows.

When stakes are high — passport risk, license suspension, contempt, or six-figure balances — run the calculator, then confirm with your county LCSA or counsel. Alameda County's LCSA portal at https://acgov.org/cs is an example of where to open a case or request payment history; your county's site may differ, but the workflow is similar statewide.

California Enforcement Tools: Beyond Interest Accrual

Interest at 10% under Cal. Fam. Code § 17433.5 is only one part of what makes California child support arrears expensive. The Local Child Support Agency (LCSA) — and private parties in appropriate cases — have broad enforcement tools that operate on the principal debt whether or not interest has been fully adjudicated on the account.

Wage withholding (income assignment). California routinely enforces support through earnings withholding orders sent to employers. When arrears exist, withholding amounts can include current support plus an amount toward arrears. Federal law caps ordinary garnishments for consumer debts much lower than support; child support withholding can take a larger slice of disposable earnings, especially when a parent is more than twelve weeks in arrears under federal rules referenced in interstate enforcement practice.

Federal and state tax refund intercept. Past-due child support can be certified for federal tax refund offset. California also intercepts state tax refunds. A parent expecting a large refund may instead see it applied to arrears — principal and, where applicable, interest and fees.

License suspension — driver's and professional. California participates in license suspension programs for child support delinquency. Driver's licenses and professional or occupational licenses can be suspended when support goes unpaid, which is particularly devastating for parents who need to drive to work or must maintain professional credentials to earn the income needed to catch up.

Passport denial. Under federal law, child support arrears exceeding $2,500 can trigger passport denial or revocation through the federal passport denial program. This affects parents who travel for work, family abroad, or planned vacations — often the enforcement hit that finally forces engagement.

Property liens. Child support judgments and arrears can become liens on real property in appropriate cases, complicating sales, refinances, and equity access.

Bank levies. Once enforcement reaches levy stage, financial institution accounts can be tapped up to applicable limits after notice requirements. This is not the first tool, but it is on the table in serious delinquency.

Credit reporting. Arrears reporting damages credit, affecting housing, employment background checks, and borrowing costs long after the family case feels "old."

Contempt and criminal nonsupport pathways. Willful failure to pay when ability exists can lead to contempt in family court — with coercive sanctions — and, in egregious cases, criminal exposure under California's nonsupport statutes. Interest continues accruing while these processes unfold unless and until payments cure the underlying installments.

Why enforcement matters to interest strategy. A paying parent focused only on the 10% rate may underestimate the cost of frozen passports and suspended licenses. A custodial parent focused only on enforcement may underestimate the value of formally requesting interest if it is not already on the account. Both numbers — growing principal plus statutory interest, and enforcement risk — belong in the same conversation.

If you are navigating enforcement, start with your county LCSA — for example, Alameda County at https://acgov.org/cs — to confirm balances, withholding percentages, and license hold status. Bring payment histories to every meeting. Enforcement staff work from official records, not informal text agreements.

The LCSA's Role: When Interest Is and Isn't Automatic

California's 58 county Local Child Support Agencies enforce most child support cases with state and federal funding under Title IV-D. The LCSA is often the custodial parent's best collection arm — but LCSA accounting and interest adjudication are not identical concepts. Understanding when interest runs automatically on the agency ledger versus when someone must request it saves both sides from expensive surprises.

What LCSAs routinely do. Open or enforce cases, establish parentage and orders, locate obligors, issue income withholding orders, collect through the State Disbursement Unit, pursue tax intercepts, and invoke license suspension and passport referral when thresholds are met. They maintain official payment histories that courts and both parties rely on in contempt and modification proceedings.

When interest appears on the official balance. In many IV-D cases with formal arrears determinations, statutory interest under Cal. Fam. Code § 17433.5 is calculated and reflected on agency statements once the arrears infrastructure exists — particularly after judicial or administrative arrears adjudication. The 10% simple rate from each payment's due date is the legal measure agencies use when interest is active on the account.

When interest is not automatic — informal agreements and private cases. Parents who handle support privately — direct payments, Venmo, or informal "we'll skip summer" deals without order modifications — may have arrears principal that nobody has ever asked a court or LCSA to compute with interest. Statutory interest rights exist under § 17433.5, but getting interest onto an enforceable balance often requires the creditor — custodial parent or LCSA acting on their behalf — to request adjudication. Interest does not magically attach because a parent "feels" owed; the procedural pathway must run.

Creditor must request in many non-IV-D pathways. If you opted out of full LCSA services or never opened a IV-D case, you may need private counsel to file a motion to determine arrears and interest. The request should attach a due-date ledger and ask the court to apply 10% simple interest per payment from each due date. Waiting years to request interest does not erase interest that already accrued statutorily — but it can delay enforcement of the interest portion if it was never reduced to an order or agency determination.

Paying parents: do not assume "no interest on the statement" means "no interest ever." It may mean interest was not yet adjudicated or applied in that system. A later successful request can produce a larger balance than you expected. If you are negotiating payoff, ask explicitly whether the figure is principal-only or principal-plus-interest, and get the answer in writing through a stipulation or order.

Custodial parents: do not assume LCSA is maximizing every dollar automatically. Agency priorities, case type, and staffing affect timing. If your case is private and arrears are large, ask the LCSA whether IV-D services are available or whether you should file for arrears and interest determination. Bring your payment ledger.

Modification vs. interest. Lowering future support through a modification does not erase accrued arrears or interest on amounts due under the old order. The LCSA will enforce the existing balance unless a court orders otherwise in a lawful compromise.

Interstate cases. If the obligor moved out of California, UIFSA mechanisms still allow enforcement — but interest calculations should follow California law for California orders when California law governs the interest question. Coordinate with both states' agencies early.

Resources. County LCSA websites — such as https://acgov.org/cs for Alameda — provide forms, employer services, and balance inquiry pathways. Statutory text lives at https://leginfo.legislature.ca.gov. For installment-level math before you call the agency, use /child-support-arrears-interest-calculator/california.

Low Income Adjustment and Arrears: What Changes and What Doesn't

California's Low Income Adjustment (LIA) can reduce a parent's ongoing child support obligation when net disposable income falls below guideline thresholds — commonly discussed around roughly $1,700 per month net in planning conversations, though exact worksheet results depend on the case facts and current guideline materials. Parents behind on support sometimes hope LIA will shrink everything they owe, including interest. It does not work that way.

What LIA changes. LIA affects the guideline calculation for current and prospective support — potentially lowering the monthly amount a low-income obligor must pay going forward when statutory criteria are met. That can prevent new arrears from accumulating at the old rate after a successful modification or LIA finding tied to updated income proof.

What LIA does not change — already-accrued interest. Interest under Cal. Fam. Code § 17433.5 that has accrued on unpaid installments from their original due dates is statutory simple interest on historical principal. A low-income adjustment today does not erase interest that already stacked on missed payments from prior years. The clock that started in 2022 on a missed March payment keeps its history even if 2026 income qualifies for LIA on current support.

What LIA does not erase — vested arrears principal. Arrears are past-due support under prior orders. Modification and LIA reorient the future; they do not automatically forgive principal unless a court orders a lawful compromise or rare discharge scenario. If you owed $18,000 in principal arrears before LIA, that $18,000 generally remains collectible — subject to enforcement discretion and negotiation — even if your ongoing monthly number drops.

Interaction effect — still important for struggling parents. LIA can free cash flow so a parent can finally pay current support and begin retiring oldest arrears, which stops the longest simple-interest clocks. A parent who qualifies for LIA but never files for modification may continue accumulating new arrears at the old rate — the worst of both worlds.

Interaction effect — custodial parent perspective. LIA is not bad faith; it is statutory recognition that extracting blood from stone does not feed children. But it also means collection strategy must separate "fight about future rate" from "collect past due principal and interest." Those are different motions, different negotiations, and different LCSA conversations.

Documentation LIA requires. Pay stubs, tax returns, unemployment records, and proof of other household obligations. Without clean income proof, courts cannot apply the adjustment you believe you deserve — and you may keep paying — or not paying — based on outdated numbers.

Arrears payment plans alongside LIA. Courts and LCSAs sometimes combine lowered ongoing support with an explicit arrears payment plan — for example, current reduced amount plus $50 or $100 per month toward back support. Interest continues to accrue on unpaid principal slices until paid unless a negotiated payoff order says otherwise within lawful bounds.

Bankruptcy misconception. Child support arrears and related interest are generally nondischargeable in bankruptcy. LIA is not a bankruptcy substitute.

If net income is near the LIA threshold, run both calculations: support with and without LIA, and arrears interest under § 17433.5 on the existing ledger. TheLegalCalc tools help model the arrears side; LIA itself requires the official California guideline worksheet or counsel.

California vs Other States: How Arrears Interest Compares

California's child support arrears interest model — 10% simple interest from each payment's due date under Cal. Fam. Code § 17433.5, aligned with CCP § 685.010 — is clearer than many states' rules but not the harshest nationwide. Comparing states helps relocating parents, interstate cases, and anyone wondering whether "interest always works this way."

California — 10% simple, per-payment due dates. Automatic statutory rate tied to judgment interest; installment-by-installment accrual; no compounding under the basic Family Code framework. Complexity is logistical (many clocks), not algebraic (compound exponents).

Texas — interest exists but case pathways differ. Texas Family Code provisions allow interest on overdue child support in enforcement contexts, but practice and adjudication timing differ from California's long-running 10% simple per-due-date culture. Always verify Texas's current rate and whether interest attaches from delinquency or from a specific determination.

Illinois — major 2024 shift. Illinois historically added 9% interest automatically in many contexts; recent reforms require many creditors to petition for interest rather than receiving it automatically. California remains more uniformly statutory at 10% once interest applies, while Illinois shifted toward opt-in interest adjudication.

Indiana — 8% simple interest commonly cited on arrears with strong enforcement and no statute of limitations on collection in practice discussions. Lower rate than California, but still meaningful over long horizons.

New York — interest on child support judgments and arrears under CPLR and Family Court Act frameworks at rates that have varied over time and may differ from California's flat 10% judgment alignment. New York practice is heavily docket-driven.

Florida — statutory interest on overdue support with rates tied to statutory judgment interest frameworks that can change; enforcement through Department of Revenue and clerks of court. Compare due-date vs. judgment-date accrual rules carefully in interstate cases.

States with minimal or conditional interest. Some states impose no statutory interest unless a court orders it, or cap interest aggressively. Zero-interest states are not "free passes" — enforcement tools still apply to principal.

Why comparison matters practically. A parent who moved from California to Nevada or Arizona may assume the old state's interest rules still govern a California order — often true for interest on California orders under UIFSA choice-of-law analysis, but enforcement happens locally. A custodial parent owed support from an out-of-state obligor needs both states' agencies coordinated.

Rate vs. structure. A state with 12% compound would outrun California quickly. A state with 6% simple might look softer until you notice faster license suspension or felony nonsupport thresholds. Evaluate rate, simple vs. compound, due-date vs. judgment-date, and whether interest requires a petition.

California's distinctive twist is per-payment simple accrual at a judgment-aligned 10%. That combination is easy to describe and hard to calculate without tools — which is why national one-size-fits-all arrears calculators often fail for California specifically.

Use /child-support-arrears-interest-calculator/california for California orders. For statutory research comparisons, https://leginfo.legislature.ca.gov remains the authoritative California source.

California Courts and the Calculator

California child support arrears interest sits at the intersection of family law practice, LCSA enforcement machinery, and straightforward-but-tedious math. You do not need to choose between understanding the law and running the numbers — you need both, in that order.

Statutory sources. Read Cal. Fam. Code § 17433.5 for the child support interest rule and CCP § 685.010 for the judgment interest rate California uses as the benchmark. Official codified text is published at https://leginfo.legislature.ca.gov without paywalls or login barriers. Search "Family Code 17433.5" or "Code of Civil Procedure 685.010" directly.

Local Child Support Agency. Your county LCSA is the operational hub for withholding, balance histories, tax intercept referrals, and license enforcement. If you are in Alameda County, start at https://acgov.org/cs for case services, payment options, and employer withholding information. Other counties host parallel sites through the California Department of Child Support Services directory — search your county name plus "child support services."

Court forms and self-help. California courts publish family law forms for motions to determine arrears, contempt, and modification. Self-help centers can explain which form fits which problem — but they cannot replace legal advice on large interest balances or criminal exposure risk.

TheLegalCalc California arrears interest calculator. Before you call an attorney or sit down with LCSA enforcement staff, model your balance using installment logic at /child-support-arrears-interest-calculator/california. Enter missed payments with due dates, partial payments, and a calculation date. Compare the calculator output to agency statements line by line. If they diverge, you have a focused question instead of a generic dispute.

When to escalate to counsel. Contempt, passport holds, property liens, six-figure balances, disputed paternity or order validity, or LIA/modification fights that touch arrears all deserve licensed California family law advice. The calculator and this guide narrow the conversation; they do not replace it.

When to escalate to LCSA. Open or convert to a IV-D case if you are owed support and need tax intercept, wage assignment, or license tools. Provide employer addresses, bank leads if permitted, and a clean payment history. If you owe support, engage before passport denial — reversal takes time even after payment.

Documentation checklist. Current order PDF; all stipulations; SDU/LCSA printouts; bank records matching withholdings; proof of informal payments that never hit the official account; calendar of due dates; prior modification orders splitting old vs. new rates.

Payment strategy reminder. Retire oldest arrears first to kill the longest-running 10% simple clocks. Keep current support current to avoid stacking new timers. Never rely on informal side deals without a signed order modification.

California's 10% simple interest from each due date is predictable law with unpredictable human behavior around it — missed modifications, informal skips, job changes, and multi-state moves. Use the statute, the agency, and the calculator together so your plan matches how California actually enforces arrears.