Overdue invoice interest calculator
Enter the invoice amount, the interest rate and how many days it's past due to see the interest owed and the total due today. At 18% a year, a $2,500 invoice that's 60 days late has built up about $74 in interest.
How it's calculated
Simple interest, the way most invoices charge it: amount × annual rate ÷ 365 × days late. A monthly rate is turned into an annual one (× 12) first.
Questions
How do you calculate interest on an overdue invoice?
Multiply the invoice amount by the annual rate, divide by 365 to get the daily interest, then multiply by the number of days late. For $2,500 at 18%: $2,500 × 0.18 ÷ 365 = $1.23 a day.
What interest rate can I charge on late invoices?
Whatever your contract allows, up to your state's legal limit. Many states also set a statutory rate for unpaid debts when the contract doesn't name one. Check your state's rules before choosing a rate.
Is it a late fee or interest?
A late fee is usually a set charge (a flat amount or a percentage, once or per month). Interest builds every day the balance is unpaid. Some businesses use one, some both; your terms should say which.
Should I charge interest to a good client?
Many businesses put interest in their terms and waive it for a client who pays as soon as they're reminded. The terms give you leverage without forcing you to use it.
Get paid without chasing
Casey is an AI accounts receivable assistant. It sends your invoices, reminds clients before the due date and follows up after it by email, text, WhatsApp or phone until you're paid. It's free when clients pay on time. See how it works or read our guides on getting paid faster.
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