Free calculator
Late fee
calculator
A late fee is an extra charge on a payment made after its due date. Enter the overdue amount, how late it is and the rate or fee you agreed, and see the charge and the new total. No signup, and nothing leaves your browser.
Calculated late charge
Enter the amount, the dates and your agreed rate or fee to see the late charge.
For monthly rates, this calculator treats every 30 days as one month and prorates the rate by day. Annual rates use a 365-day year. All percentage calculations use simple interest. Charges are not compounded.
Published · By RecordSplit
How it works
How the late charge
is calculated.
Four steps, with nothing hidden: how late the payment is, which method your terms use, the rate or fee you agreed, then the arithmetic.
- 1. Days overdue
- Count the calendar days from the due date to the payment date, or to today if the invoice is still unpaid. Paid on or before the due date means 0 days and no charge.
- 2. Your method
- Pick the method your agreement uses: a flat fee, a one-time percentage, a monthly percentage or an annual percentage.
- 3. Your rate or fee
- Enter the rate or fee you agreed with your customer. The calculator doesn't suggest one.
- 4. The charge
- The calculator works out the charge exactly, rounds it once to the nearest cent, and adds it to the amount to give the total.
Four methods
Flat fee vs percentage
vs interest.
A flat fee or one-time percentage is charged once. Monthly and annual percentages work like simple interest: the longer the invoice is overdue, the larger the charge.
- Flat fee
- Late charge = flat fee. A fixed amount, such as $50, charged once the payment is at least 1 day late. It doesn't grow with time.
- One-time percentage
- Late charge = amount × rate. A percentage of the amount, charged once. 5% of $1,000 is $50 whether the payment is 1 day or 100 days late.
- Monthly percentage
- Late charge = amount × monthly rate × days overdue ÷ 30. Grows each day the invoice is late, like interest quoted per month.
- Annual percentage
- Late charge = amount × annual rate × days overdue ÷ 365. Grows each day the invoice is late, like interest quoted per year.
Monthly rates
The monthly
late fee formula.
Late charge = amount × monthly rate × days overdue ÷ 30
For monthly rates, this calculator treats every 30 days as one month and prorates the rate by day. At 2% a month, $1,000 that's 15 days late gives $10, 30 days late gives $20, and 45 days late gives $30. It doesn't round up to whole or started months.
For monthly rates, this calculator treats every 30 days as one month and prorates the rate by day. At 2% a month, $1,000 that's 15 days late gives $10, 30 days late gives $20, and 45 days late gives $30. It doesn't round up to whole or started months.
Annual rates
The late payment
interest formula.
Late charge = amount × annual rate × days overdue ÷ 365
Annual rates use a 365-day year, including in leap years. All percentage calculations use simple interest. Charges are not compounded, so interest is never charged on interest. $10,000 at 12% a year for 365 days is exactly $1,200.
Annual rates use a 365-day year, including in leap years. All percentage calculations use simple interest. Charges are not compounded, so interest is never charged on interest. $10,000 at 12% a year for 365 days is exactly $1,200.
Counting days
How days overdue
are counted.
Days overdue are the calendar days from the due date to the payment date (or today, if it's unpaid). Never less than 0.
- The first overdue day
- The calendar day after the due date. Due October 1 and paid October 2 is 1 day overdue.
- Every calendar day counts
- Weekends and public holidays count like any other day. The calculator doesn't move dates or count business days.
- Paid on time
- A payment on or before the due date is 0 days overdue, so every method gives a late charge of $0.
- Already know the number?
- Switch to "Enter days overdue" and type it: a whole number from 0 to 3,650. That limit is only how far this tool counts.
Partial payments
If part of the invoice
has been paid.
If part of an invoice has already been paid, enter the balance your agreement says the late charge applies to. If payments were made over time, calculate from the amount your agreement says the charge applies to. This tool does not reconstruct changing balances across multiple payment dates.
Your terms, your rate
What the calculator
does and doesn't decide.
It does the arithmetic for the terms you enter. Whether those terms apply is for your agreement and the law where you do business.
- Your rate, applied as entered
- This calculator applies the rate or fee you enter. It does not determine whether a late fee or interest charge is allowed under your contract or local law.
- What it doesn't look up
- It doesn't supply statutory rates, check state limits or usury caps, or say whether a fee is enforceable. It doesn't recommend a rate.
- Agree terms in advance
- Late charges usually come from terms agreed before the work or sale, such as a clause in the contract or in the payment terms on your invoice. What your terms say is what to enter.
- Grace periods
- There's no grace-period setting. If your terms only start the charge after a grace period, enter the date the charge begins as the due date, or adjust the days overdue yourself.
- Not legal advice
- If you're unsure what you can charge, check your agreement and ask a qualified adviser where you do business.
Worked example
One overdue invoice,
four methods.
An invoice for $1,000 was due Thursday, October 1, 2026 and paid Saturday, October 31, 2026. That's 30 days overdue: October 2 is day 1 and October 31 is day 30.
The right-hand column shows the late charge under four example terms. At 18% a year: $1,000 × 0.18 × 30 ÷ 365 = $14.7945…, which rounds to $14.79, for a total of $1,014.79. These rates are examples only, not suggestions.
- Flat fee of $50
- $50.00
- One-time 5%
- $50.00
- 2% a month
- $20.00
- 18% a year
- $14.79
- Paid on Oct 1 (on time)
- $0.00
Each charge is added to the $1,000 to give the total. At 2% a month the same invoice 15 days late would be $10.00.
In RecordSplit
See what's overdue
before you calculate.
In RecordSplit's invoicing, you create invoices with a due date and record payments in full or in part as they arrive. Receivables lists unpaid and partially paid invoices by customer and by how many days past due they are, and you can send a payment reminder when you choose; nothing is sent automatically. For the wording of the follow-up itself, see these overdue payment reminder emails; they mention a late fee only where your agreed terms include one. RecordSplit doesn't calculate, add or charge late fees or interest, and it doesn't collect card payments. Use this calculator for the arithmetic of the terms you agreed.
Late fee questions
How do I calculate a late fee on an invoice?
Use the method in your agreement. A flat fee is charged once. A one-time percentage is the amount × the rate. A monthly rate is the amount × the rate × days overdue ÷ 30, and an annual rate is the amount × the rate × days overdue ÷ 365. $1,000 at 2% a month, 15 days late, is $10.
How do I calculate late payment interest?
With simple interest at an annual rate: amount × annual rate × days overdue ÷ 365. $1,000 at 18% a year, paid 30 days late, is $1,000 × 0.18 × 30 ÷ 365 = $14.79, rounded to the nearest cent.
How is a monthly late fee prorated?
For monthly rates, this calculator treats every 30 days as one month and prorates the rate by day. 45 days late at 2% a month is 1.5 months, so $1,000 gives $30.
What late fee or interest rate should I charge?
This calculator doesn't recommend a rate. Use the rate or fee in the terms you agreed with your customer. What you can charge depends on your agreement and the law where you do business.
Does the calculator compound interest?
No. All percentage calculations use simple interest. Charges are not compounded: each day's charge is worked out on the amount you enter, never on charges already added.
What if the customer has already paid part of the invoice?
Enter the balance your agreement says the charge applies to. If payments were made over time, calculate from the amount your agreement says the charge applies to. This tool does not reconstruct changing balances across multiple payment dates.
Does it handle a grace period?
No. If your terms start the charge only after a grace period, enter the date your agreed charge begins as the due date, or reduce the days overdue yourself.
Does the annual method use 366 days in a leap year?
No. Annual rates use a 365-day year every year, so a full leap year of 366 days gives slightly more than the annual rate.
Does RecordSplit add late fees to invoices?
No. RecordSplit doesn't calculate, add or charge late fees or interest, and it doesn't collect card payments. It records the invoices you issue and the payments you receive, and shows how many days past due each unpaid invoice is.
Is anything I enter saved or sent anywhere?
No. The calculation runs in your browser. The amount, dates, rate, fee and result aren't stored, put in the page address or sent to RecordSplit.
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