Late Fee Calculator
Estimate what an overdue invoice should total after percent and/or flat late fees.
Calculator
e.g. 1.5% of the invoice (one-time, or per month if compounding).
Results
Late fee
$37.50
Total amount due
$2,537.50
What this means
Late fees can nudge payment but aren’t a collections strategy by themselves. Prefer deposits and clear Net terms.
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Late Fee Summary
Late fees can be a one-time percent and/or flat amount, or repeated each month past due. Total due = invoice + accumulated late fees under the rules you choose.
Explanation
Late fee is the extra amount from your percent and/or flat structure.
Total amount due is the original invoice plus that fee.
Business implication: clear, enforceable terms beat surprise penalties—and still use late fees as a prompt, not your profit model.
Step-by-step example
Invoice $2,500, 15 days late, 1.5% one-time fee:
- Fee: $2,500 × 0.015 = $37.50
- Total due: $2,537.50
Formula
One-time: Fee = Amount × Percent + Flat
Monthly: each 30-day period adds Percent × balance + Flat
Total due = Amount + Fee
Helpful tips
- Disclose late fees on proposals and invoices before work starts.
- Follow up politely before fees—relationships often collect faster than penalties.
FAQ
Are late fees legal?
It depends on your jurisdiction and contract. Many places allow reasonable, disclosed late fees; usury or consumer rules can limit them. This tool does the math only—not legal advice.
What is a typical late fee?
Common B2B patterns include a flat fee, a small monthly percentage (e.g. 1–1.5%), or both—if allowed by the agreement and law.
How does monthly compounding work here?
Days late are grouped into 30-day periods (rounded up). Each period applies your percent to the growing balance and adds any flat fee again.
How accurate is this calculator?
It follows the fee structure you enter. Your contract may define grace periods, caps, or different compounding—match those inputs carefully.
Related tools
Key terms
Late fee
Definition. An extra charge applied when payment arrives after the due date, according to your terms and applicable rules.
In simple terms. Late fees can encourage on-time payment, but they must be disclosed and legally allowed. They are not a substitute for deposits and clear scope.
Late fee ≈ overdue amount × late fee rate (or a fixed fee, per your terms)
Example. A $2,000 invoice 15 days late at 1.5%/month (if allowed and disclosed) is modeled differently than a flat $25 fee.
Common mistake. Adding surprise fees that were never in the contract or invoice terms.
Related calculators. Late Fee Calculator, Invoice Due Date Calculator
Related terms. Invoice due date, Accounts receivable days
Invoice due date
Definition. The date payment is expected under your payment terms (Net 15, Net 30, due on receipt, etc.).
In simple terms. Clear due dates set collection expectations. They also feed cash-flow forecasts and late-fee policies.
Due date = invoice date + payment terms (in days)
Example. Invoice dated March 1 on Net 30 is due March 31.
Common mistake. Sending invoices without stated terms, then arguing about “late.”
Related calculators. Invoice Due Date Calculator, Late Fee Calculator
Related terms. Late fee, Accounts receivable days, Cash flow
Accounts receivable days
Definition. How many days, on average, it takes to collect payment after a sale on credit.
In simple terms. Higher AR days mean more of your money sits in unpaid invoices. That affects runway and whether you need deposits or tighter terms.
AR days ≈ (accounts receivable ÷ revenue) × days in period
Example. If AR is $30,000 and monthly revenue is $45,000, AR days are roughly 20 on a 30-day basis (simplified).
Common mistake. Ignoring aging—averages can hide a few very late invoices.
Related calculators. Accounts Receivable Days Calculator, Invoice Due Date Calculator
Related terms. Cash flow, Invoice due date, Late fee
Notes & Assumptions
Late-fee practices vary by contract and local law. Confirm with counsel if you operate across states or consumer clients.
Last reviewed: July 2026