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Finance · Free browser tool

Invoice Late Fee & Net Terms Calculator

Calculate invoice due dates, days overdue, late payment interest fees, and total amount owed instantly.

Invoice details

Results update instantly as you type.

Payment terms
Late fee structure

A late fee is generally only enforceable if your contract or invoice terms disclosed the rate before work began. This calculator is a planning estimate, not legal advice—confirm your local usury laws before charging interest on unpaid invoices.

Payment due date

—

Net 30

Status

Not overdue

0 day(s) until due

Total late fees

$0.00

18.0% APR

Total amount due

$2,500.00

Invoice amount + late fee

Payment breakdown

Invoice amount
$2,500.00
Payment terms
Net 30
Due date
—
Annual APR % late fee (18.0% APR)
$0.00
Total amount due
$2,500.00

Late fee notice clause

Copy this wording into a payment reminder email or your invoice terms section to formally disclose the fee being applied.

This invoice is governed by Net 30 payment terms, with payment due on —. Late payments accrue a late fee of 18.0% APR for each day the balance remains unpaid past the due date.

Frequently Asked Questions

What do payment terms like Net 15, Net 30, or Net 60 actually mean?

"Net" followed by a number of days means the invoice is due that many days after the invoice date—Net 30 is due 30 days after issue, not 30 days after the client receives or opens it. These terms set the payment due date this calculator uses as the baseline for determining whether an invoice is overdue and, if so, by how many days.

What is a reasonable late fee rate to charge?

Many freelancers and small businesses charge a monthly late fee of 1–2% (roughly 12–24% APR), which is a common range in US commercial contracts, though some jurisdictions cap interest rates on certain agreements—check your local usury laws. Others prefer a flat fee (e.g., a fixed $25–$50 charge) for simplicity. Whichever structure you choose, the rate only matters if it's actually enforceable.

How do I make a late fee legally enforceable?

A late fee is generally only enforceable if it was clearly disclosed to the client before the work began—ideally written into your contract, statement of work, or the invoice's payment terms section itself, stating the exact rate or flat amount and when it starts accruing. Surprising a client with a late fee they never agreed to is far less likely to hold up if disputed. This tool's "Copy Late Fee Notice" button generates wording you can adapt into your invoice terms or a payment reminder.

Is my invoice or client data uploaded anywhere?

No. Every date calculation and fee estimate runs locally in your browser—your invoice amounts, dates, and client details are never sent to a server.

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Net Terms, Due Dates, and Late Fees: A Freelancer's Guide to Getting Paid on Time in 2026

"Net 30" is one of the most misunderstood phrases on a small business invoice. It does not mean 30 days after the client reviews the work or 30 days after they receive the invoice in their inbox—it means the payment is due 30 days after the invoice date itself. The same logic applies to Net 15, Net 60, and Net 90: the due date is simply the invoice date plus that many calendar days. Getting this baseline right matters, because everything downstream—whether an invoice is overdue, and by how much—depends on calculating it correctly.

Once an invoice passes its due date, a late fee can be applied in one of a few common ways. An annual APR (commonly 12–24% in US commercial practice) is prorated by the number of days overdue divided by 365. A monthly rate—often 1–2%—is prorated by days overdue divided by 30, which tends to compound faster than an equivalent-sounding APR. Some businesses skip percentage math altogether and apply a flat fee, such as a fixed $25–$50 charge, the moment an invoice becomes overdue. None of these are one-size-fits-all; check local usury law limits before setting a high interest rate on outstanding invoices.

The single biggest factor in whether a late fee actually gets paid is whether the client agreed to it beforehand. A rate buried nowhere or invented after the fact is far easier to dispute than one written into your contract, statement of work, or the payment terms section printed on the original invoice. That is why this calculator includes a ready-to-copy late fee notice clause—use it to make your payment terms explicit up front, or to formally document an overdue charge in a payment reminder email.

For freelancers pricing new work, it is worth cross-checking whether your day rate already accounts for the cash-flow risk of slow-paying clients—the Freelance Hourly Rate Calculator can help you build that buffer into your baseline rate rather than relying solely on late fees to make up the gap. This free Invoice Late Fee & Net Terms Calculator runs entirely in your browser—your invoice amounts, dates, and client details are never uploaded to a server.