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ToolsInterest owed on late invoices

How much interest is owed on your late invoices?

For firms that invoice from Xero. Drop your sales invoices export, type the yearly rate your terms set, and see the interest on every invoice past its due date, with every sum shown. A calculation at your rate, not advice on what you may charge.

Sample invoices, October to September

A small Brisbane electrical firm’s Xero invoices, all made up for this demo

Your rate and date

Type the yearly rate your terms set. A monthly rate times 12 is the yearly one, so 1.5% a month is 18% a year.

Interest owed on late invoices

$190.04

9 of your invoices are past their due date with $30,169.02 still owed, and at the 8% a year you set, that is $190.04 of interest up to 30 September 2026, $111.00 of it on Brennock Builders’ 3 invoices.

$30,169.02 still owed = the amount due on 9 late invoices, added up. $190.04 of interest = each late invoice’s interest added up, each one its amount due × 8% a year × its days late ÷ 365. $111.00 for Brennock Builders = $69.73 on INV-2298 + $29.59 on INV-2287 + $11.68 on INV-2340. Interest is on what each customer still owes. If they paid part of an invoice late, the interest on that part is not counted.

Every customer with a late invoice, most interest first

Customerhow many late invoicesStill owedon its late invoicesLongest latedue date to 30 Sep 2026Interestits invoices’ interest added upShare of all the interestits interest ÷ all of it
Brennock Builders3 late invoices$15,870.65$5,215.45 on INV-2298
+ $1,776.59 on INV-2287
+ $8,878.61 on INV-2340		76 daysINV-2287, due 16 Jul 2026$111.00$69.73 on INV-2298
+ $29.59 on INV-2287
+ $11.68 on INV-2340		58.4%$111.00 ÷ $190.04 all the interest
Little Wren Coffee2 late invoices$2,769.90$2,254.49 on INV-2262
+ $515.41 on INV-2324		124 daysINV-2262, due 29 May 2026$65.22$61.27 on INV-2262
+ $3.95 on INV-2324		34.3%$65.22 ÷ $190.04 all the interest
Tamsett Building Co1 late invoice$8,470.595 daysINV-2342, due 25 Sep 2026$9.284.9%$9.28 ÷ $190.04 all the interest
Tomasz Vukovic1 late invoice$663.9221 daysINV-2346, due 9 Sep 2026$3.061.6%$3.06 ÷ $190.04 all the interest
Haddow Property Management1 late invoice$290.6316 daysINV-2344, due 14 Sep 2026$1.020.5%$1.02 ÷ $190.04 all the interest
Joanne Hale1 late invoice$2,103.331 dayINV-2360, due 29 Sep 2026$0.460.2%$0.46 ÷ $190.04 all the interest
All 6 customers9 late invoices$30,169.026 customers added up124 daysINV-2262, due 29 May 2026$190.046 customers added upAll of it

Every late invoice, most interest first

Invoicenumber and the day it was raisedCustomerDays latedue date to 30 Sep 2026Still owedits amount dueIntereststill owed × 8% × days ÷ 365
INV-2298raised 1 Jul 2026Brennock Builders61 daysdue 31 Jul 2026$5,215.45the whole invoice$69.73$5,215.45 × 8% × 61 days ÷ 365
INV-2262raised 15 May 2026Little Wren Coffee124 daysdue 29 May 2026$2,254.49the whole invoice$61.27$2,254.49 × 8% × 124 days ÷ 365
INV-2287raised 16 Jun 2026, not marked as sent in XeroBrennock Builders76 daysdue 16 Jul 2026$1,776.59$5,921.98 invoice
− $4,145.39 paid		$29.59$1,776.59 × 8% × 76 days ÷ 365
INV-2340raised 25 Aug 2026, not marked as sent in XeroBrennock Builders6 daysdue 24 Sep 2026$8,878.61the whole invoice$11.68$8,878.61 × 8% × 6 days ÷ 365
INV-2342raised 26 Aug 2026Tamsett Building Co5 daysdue 25 Sep 2026$8,470.59the whole invoice$9.28$8,470.59 × 8% × 5 days ÷ 365
INV-2324raised 12 Aug 2026, not marked as sent in XeroLittle Wren Coffee35 daysdue 26 Aug 2026$515.41the whole invoice$3.95$515.41 × 8% × 35 days ÷ 365
INV-2346raised 2 Sep 2026Tomasz Vukovic21 daysdue 9 Sep 2026$663.92the whole invoice$3.06$663.92 × 8% × 21 days ÷ 365
INV-2344raised 31 Aug 2026Haddow Property Management16 daysdue 14 Sep 2026$290.63$392.74 invoice
− $102.11 credited		$1.02$290.63 × 8% × 16 days ÷ 365
INV-2360raised 22 Sep 2026, not marked as sent in XeroJoanne Hale1 daydue 29 Sep 2026$2,103.33the whole invoice$0.46$2,103.33 × 8% × 1 day ÷ 365

What this counts

  • An invoice is late when it is awaiting payment, has an amount due, and its due date is before the day you count up to.
  • Interest is simple interest by the day, the amount due × your yearly rate × days late ÷ 365, in every year. Each invoice’s interest is rounded to the cent, then added up.
  • The amount due is what Xero says is still owed on the day you exported. Payments and credit notes set against an invoice are already taken off it.
  • Each invoice counts once, however many lines it has in the file.
  • Paid invoices are left out, as the file has no date they were paid. So are drafts, invoices awaiting approval and credit notes.
  • An invoice not marked as sent in Xero counts like the rest, as Xero’s own overdue list counts it, and the table says so.

Also in your file

  • 11 invoices awaiting payment are not due yet, $19,274.30 still owed, the next due on 5 October 2026.
  • 4 late invoices are not marked as sent in Xero. They count like the rest.
  • 245 invoices are paid, so nothing is owed on them.
  • 3 invoices are marked Draft, not Awaiting Payment, so they are not counted.
  • 4 credit notes are not counted. One set against an invoice is already taken off that invoice’s amount due.

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