How to Calculate Child Support Arrears
What is Child Support Arrears?
A child support arrears calculator computes the total amount of unpaid child support plus any interest or penalties that have accrued. Arrears accumulate when a parent fails to make court-ordered payments on time, and most states charge interest on the unpaid balance.
Formula
Total Arrears = Sum of Missed Payments + (Unpaid Balance × Interest Rate × Time)
- P
- Monthly Obligation ($/month) — Court-ordered monthly child support amount
- n
- Months Unpaid (months) — Number of months with missed or partial payments
- r
- Interest Rate (%/year) — State statutory interest rate on arrears (varies 6–12%)
Step-by-Step Guide
- 1Identify the monthly support obligation and the months of non-payment or underpayment
- 2Calculate the base arrears by summing all missed or short payments
- 3Apply the state’s statutory interest rate to the running unpaid balance
- 4Add any penalties, processing fees, or contempt-of-court fines
Worked Examples
Input
$800/mo obligation, 18 months unpaid, 10% annual interest
Result
Base arrears $14,400 + ~$1,080 interest = ~$15,480 total
Input
$500/mo obligation, partial payments of $300/mo for 12 months
Result
Base arrears $2,400 + interest on running balance
Common Mistakes to Avoid
- ✕Assuming arrears go away when the child turns 18 — they do not; the debt persists until paid
- ✕Not realizing interest compounds on the running balance, not just the original amount
- ✕Failing to file for modification during hardship, causing arrears to accumulate
Frequently Asked Questions
Can child support arrears be forgiven?
Arrears owed to the custodial parent can sometimes be negotiated or settled. However, arrears owed to the state (from public assistance reimbursement) are rarely forgiven.
What happens if arrears exceed $2,500?
The State Department can deny or revoke your passport if you owe more than $2,500 in child support arrears.
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