InvoiceHoundFree tool
Enter what you're owed, how late it is, and your monthly rate. See the fee that's accrued and the total now due, no account, no email wall.
The 1.5% monthly rate is an example. This calculator treats every 30 days as one month. Use the rate and method in your agreed payment terms.
Accrued late fee
$54.00
At 1.5%/month simple, a $2,400.00 invoice 45 days late has accrued $54.00.
Invoice payment terms can describe a one-time flat late fee, a percentage of the unpaid balance, or interest stated as an annual rate. Apply only the method and rate in your agreed terms. Contracts and jurisdictions differ, so ask a qualified local adviser if you are unsure whether a charge applies.
$2,400 balance + $50 flat fee = $2,450 total
A flat fee adds one fixed charge after the trigger in your agreed payment terms. This calculator does not add one-time flat fees, so add the agreed amount to the unpaid balance separately.
$2,400 balance × 2% = $48 fee
A one-time percentage fee applies the agreed rate to the unpaid balance once. The 2% rate here is only an example. This calculator models a monthly rate, so calculate a one-time percentage separately when that is what your terms specify.
$2,400 × 1.5% × (45 ÷ 30) = $54 fee
This is the calculator's default example. It treats every 30 days as one month. With Simple selected, the fee is $54 and the total owed is $2,454.
$2,400 × 18% × (45 ÷ 365) = $53.26 fee
An annual-interest term can be prorated by the exact days in a 365-day year. The calculator above accepts a monthly rate and uses 30-day months, so use this separate formula when your terms specify annual interest calculated by actual days.
There is no universal rate. Use a fee and calculation method supported by your agreed payment terms and the rules that apply where you and your client operate. The 1.5% monthly rate shown in this calculator is an illustration, not a recommendation or a statement of what is permitted.
For a simple monthly percentage fee, multiply the overdue amount by the monthly rate, then by the number of 30-day months overdue. A $2,400 invoice at an illustrative 1.5% per month for 45 days accrues $54.00. Compounding adds each period's fee to the balance before the next period is calculated.
A flat late fee adds one fixed amount, such as $50. A one-time percentage fee is based on the unpaid balance, while a recurring percentage fee or interest calculation can also depend on time overdue. Use the method stated in your payment terms. This calculator handles monthly percentage fees.
Follow the grace-period method in your agreed payment terms. If those terms exclude the grace period from fee accrual, an invoice that is 12 days past due after a 5-day grace period has 7 fee-accruing days. Other terms may delay the fee trigger but calculate from the original due date.
This tool is for estimation only and isn't legal advice.
Once you know the amount, use our payment reminder templates to follow up with a client about an overdue invoice.
Once you know what is owed, InvoiceHound can chase an invoice you have already sent and stop the reminders when it is paid.
Chase your first invoice free