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Overdue Interest & Delinquent Invoice Modeling

Free Invoice Late Fee Calculator

Calculate late fees and finance charges on delinquent invoices. Compare flat fees, monthly percentage interest (1.5%/month), and annual APR rates with customizable grace periods.

Invoice Late Fee Calculator

Flat, Percentage, Monthly & APR Overdue Interest
$
%/ mo

Late Fee Breakdown

45 Days Overdue
Original Invoice:$3,500.00
Days Delinquent:45 days
Fee Model:1.5% monthly recurring
Equivalent APR:18% APR
Calculated Late Fee:+$78.75
Updated Total Due

Original + Late Fee

$3,578.75

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Notice: Late-fee enforceability depends on written contract agreements and applicable statutory usury caps. This tool performs arithmetic only.

Monthly Recurring Interest

Standard B2B practice is 1.5% per month (18% APR), prorated based on days past the invoice due date or billing cycle.

Contract Agreement Required

You cannot unilaterally assess late penalties after delivering work unless the client agreed to the payment terms in writing beforehand.

Grace Periods Build Goodwill

Offering a 5 to 7 day grace period prevents friction caused by bank ACH transfer lags, weekend delays, or AP accounting batch schedules.

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Frequently Asked Questions

Can I legally charge a late fee on an overdue invoice?

In most commercial jurisdictions, you can only charge late payment fees or interest if the terms were explicitly agreed upon in writing (such as a signed client contract, master services agreement, or approved estimate) prior to delivering the work. Statutory usury laws also cap maximum allowable interest rates.

What is the standard commercial late fee rate?

The most common standard commercial late fee is 1.5% per month (equivalent to 18% annual APR) on outstanding overdue balances, typically triggered after a 5 to 10 day grace period. Some businesses prefer a flat fee (e.g. $25–$50) for smaller balances.

Should late fees be listed as a separate invoice or updated total?

Best practice is to issue an updated statement or revised invoice showing the original principal balance, the itemized late fee calculation with days delinquent, and the revised total balance due, accompanied by a polite reminder letter.

Does Invoza give legal advice on collections?

No. This calculator performs arithmetic and financial interest modeling only. Statutory limits, usury ceilings, and contract enforceability vary significantly by state and country. Consult qualified legal counsel for dispute resolution.