Child support arrears calculator.
What should have been paid, what was paid, and the difference. For child support or spousal support arrears. You enter the amount your order or agreement requires and the payments that were actually made. It adds up both sides, month by month, and shows the gap — including where the amount changed part way through. It doesn't decide anything; the arithmetic is the whole job.
Support arrears record
The record
What should have been paid?
Special or extraordinary expenses
What was actually paid?
What is the difference?
Prepared with the free support arrears calculator at repmyself.ca/support-arrears-calculator
This is a record of figures entered by the user. It is not legal advice and not a determination of what is owed. It does not include interest. Repmyself.ca is not a law firm and using it does not create a lawyer–client relationship. Operated by The Family Law Assistant Inc.
Your entries stay in this browser. They are kept for 24 hours so a refresh doesn't lose them, on this device and browser only, and “Clear and start again” removes them immediately. Nothing is uploaded and there is no account.
How to calculate support arrears
Arrears are arithmetic, once you know two figures. “Arrears” is the accumulated unpaid balance of a support obligation — sometimes called back support or back child support. It is the difference between what an order or agreement required over a stretch of time and what was actually paid across that same stretch.
That makes it a bookkeeping problem rather than a legal one — but only after you have both figures. The required amount comes from your own document: a court order, a separation agreement, a recalculation notice. You read the figure off it. This calculator never works that figure out for you, because working it out would mean applying the law to your circumstances, and that is a different job from adding up a column.
What should have been paid
Copy the monthly amount from your order or agreement. If it changed — a variation, a recalculation, a child ageing out — add the change and the month it started. Each amount then applies from its own date forward.
What was paid
Enter what actually arrived in each month. Leave a month blank if nothing was paid. Partial payments and overpayments both work; a month where more went in than was required reads as a credit.
The difference
Both columns are totalled and subtracted. You get the gap, a running balance month by month, and a printable record you can keep with your file or bring to a lawyer.
A blank month is not a zero
If you haven't told the calculator what was required in a given month, it leaves that month out of the totals and says so, rather than treating the requirement as nil. An assumed zero would quietly understate the total. Where nothing genuinely was required for a period — support suspended, an obligation that hadn't started — enter 0 for it. A stated zero is an answer; a blank is a gap.
What this calculator does, and what it doesn't
It adds up the figures you enter and subtracts one total from the other. That is the entire function. Being specific about the rest matters more than a disclaimer does:
- It does not work out how much support should be paid. There is no income field and no table lookup anywhere in it. The child support tables and the spousal support advisory guidelines are not consulted.
- It does not calculate interest. The figure is principal only. Which rate applies, and from when, depends on your order and your file — see below.
- It does not tell you whether arrears can be reduced, cancelled or enforced. Those are questions a court decides on the facts of a particular case.
- The result is not a legal determination. It is your own arithmetic on your own entries. The other party may keep a different record, and a court has not reviewed either one.
If the figure matters — you are about to file something, or respond to something — that is the point to get advice about your specific circumstances from a lawyer, or to contact the agency or registry involved.
Who enforces child and spousal support arrears in British Columbia, and how interest works
The arithmetic above is the same anywhere. Enforcement is not — it is provincial, and the following describes British Columbia only.
In BC, support orders and agreements can be enforced through the BC Family Maintenance Agency (BCFMA), which administers enforcement under the Family Maintenance Enforcement Act. Where a file is enrolled with the agency, it keeps the official account of what is owed and what has been paid, and it has enforcement powers a private party does not have. A record you keep yourself — including one from this calculator — is not that official account.
Interest, which this tool leaves out
BCFMA charges interest on arrears. According to the agency, the rate is the one specified in the order or agreement, and where none is specified, the prime rate — updated every six months, on 1 January and 1 July. There is a 15-day grace period after a missed payment: nothing accrues if payment arrives within 15 days of its due date, and if it does not, interest runs back to the date the payment was due. The agency also describes a default fee where a payor misses two or more payments in a calendar year, equal to one month's support up to a maximum of $400, with notice and a window to dispute before it is applied.
Those mechanics are why this calculator reports principal only. Whether interest applies to your arrears, at what rate, and from what date turns on your particular order and the history of your file. Confirm the current figures with BCFMA directly rather than relying on any calculator, this one included.
Enforcement rules and the amounts above can change. This page describes British Columbia and was last checked against the agency's published information and the Family Maintenance Enforcement Act in August 2026. Always confirm current requirements with the agency, the registry, or a lawyer.
The number is a starting point, not an outcome
Both sides of a support arrangement use a ledger like this, for opposite reasons. Neither path below is a recommendation — they are simply where the two situations usually lead.
If you are owed support
Common routes, in no particular order:
- Contacting BCFMA about enforcement, which maintains the official account and can act on it.
- Bringing the arrears before the court that made the order.
- Raising it in an existing family law proceeding.
Where a court application about support is involved, a financial statement is usually required from each party — see which financial statement applies.
If you are the payor
Common routes, in no particular order:
- Checking your own record against the agency's, if a file is enrolled.
- Responding to an enforcement step or a court application.
- Asking the court to change support going forward, or to deal with the arrears.
Whether arrears can be reduced or cancelled is a question for the court and depends on the facts — this page does not answer it. A response usually needs a financial statement too.
Where financial statements come in
Almost any court step about support brings a financial statement with it. In British Columbia which one you need depends on which court your case is in — the Provincial Court Form 4 or the Supreme Court Form F8. If you're not sure, start with which financial statement applies, or read about financial disclosure generally and how a Provincial Court family case starts.
Frequently asked
What are support arrears?
Arrears are the accumulated unpaid balance of a support obligation — the difference between what an order or agreement required over a period and what was actually paid. They are a matter of arithmetic once you know both figures.
Does this calculator work out how much support should be paid?
No. You enter the amount your order or agreement requires — you copy the figure from your own document. The calculator does not look up the child support tables, does not use income, and does not work out any entitlement. It adds up what you enter and subtracts.
Does it include interest on arrears?
No — the figure is principal only. In British Columbia, BCFMA charges interest on arrears where a file is enrolled with it, at the rate in the order or otherwise the prime rate, updated on 1 January and 1 July, with a 15-day grace period. Because the rate that applies and the date it runs from depend on your particular order and file, this tool does not attempt to calculate it.
What if the support amount changed part way through?
Add the change. Use “The amount changed on a date” and enter the new monthly amount and the month it started. Each amount applies from its own start date onward, so a variation, a recalculation, or a child ageing out is handled correctly. This is the usual reason a simple total comes out wrong.
Is the number this produces the amount legally owing?
No. It is the arithmetical difference between the figures you entered — your own record. The other party may keep a different record, a court has not reviewed it, and it does not include interest or any adjustment a court might make.
How do I work out back child support that was missed?
Set the period to cover the months in question, enter the amount your order required for each stretch of that period, then enter what was actually paid in each month. Missed months are simply months with nothing entered in the paid column. The running total shows how the balance built up, which is usually what people mean by back support or back child support.
Can I use this for spousal support arrears as well as child support?
Yes. The arithmetic is identical for child support arrears and spousal support arrears; only the label at the top of the record changes. You can keep separate records for each by clearing and starting again, or by printing one before entering the other.
Does anything I type get sent anywhere?
No. The calculator runs entirely in your browser. There is no account and nothing is uploaded. Your entries are kept in this browser for 24 hours so a refresh doesn't lose them, on this device only, and you can clear them at any time.
Can I use this in court?
It produces a printable record of your own figures, which people commonly bring to a lawyer or use to organise their own material. Whether any document is admissible or persuasive in a particular proceeding is not something this page can tell you.