Invoice Late Fee Calculator
Calculate the late fee on any overdue invoice. Plus see how much overdue invoices are costing you per year.
Free forever, no signup needed, results update instantly
Service businesses leave thousands per year on the table by not charging late fees (or charging them inconsistently). This calculator does the math two ways: simple monthly interest (the most common policy) and daily compound (more aggressive, used in commercial contracts). Plus a year-over-year view of what late fees would add to your top line if you applied them consistently.
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Your inputs
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Most service businesses charge 1.5%/month (~18% APR). Some go 2%/month (~24% APR). Check your state cap.
Many policies have a $25-50 minimum so small invoices still incur a meaningful fee.
Approximate. Smarfle's Aging Report shows this exactly.
Your results
Late fee owed (simple interest)
$36.00
Standard monthly compounding, the most common policy
Auto-charge late fees on overdue invoices
Smarfle marks invoices overdue automatically, sends polite-then-firm reminders via SMS + email, and lets you apply late fees with one click. No more chasing checks or guessing what to charge.
Free for 14 days, no credit card
How this calculation works
Two ways to compute late fees: Simple monthly interest (most common in service businesses): - Late fee = invoice amount x rate% x (days / 30) - Example: $2,400 x 1.5% x (30/30) = $36 Daily compound interest (used in commercial contracts, more aggressive): - Late fee = invoice x (1 + rate%/30)^days - invoice - Example: $2,400 x (1 + 0.0005)^30 - $2,400 = ~$36.27 (1¢ more in the first month, big difference at 90+ days) The "Annual late fee revenue" line projects what you'd add to revenue if you charged late fees consistently across all overdue invoices in your book. Most service businesses with $15-30K annually in overdue invoices generate $300-900/year in late fee revenue at 1.5%/month - a small but real margin lift, more importantly it accelerates payment. Note on legality: most US states cap consumer late fees (typical: 1.5-2% per month, or ~18-24% APR). Commercial contracts have wider latitude. Always disclose the late fee rate on the invoice itself or in your service agreement BEFORE the invoice is sent. Calling a customer to add a late fee surprise is unenforceable.
Real scenarios
Find the persona closest to yours, then click to load those numbers into the calculator.
HVAC owner, $2,400 invoice 30 days late
Standard 1.5%/month policy.
Owes $2,400 + $36 = $2,436. Small, but applied consistently across the book = $270/year in extra revenue.
Commercial plumber, large overdue
$15K invoice, 45 days late, 2% rate.
Late fee = $450. Customer gets a real signal that overdue costs them money. Most pay within 7 days of seeing the fee.
Cleaning company with chronic late payers
$30K/year in late invoices, 1.5% rate.
$450/year in late fee revenue - small. The bigger win: faster payment because customers know there's a real cost to dragging it out.
Smarfle CRM
Run this in your business, not just in a calculator
These Smarfle features close the loop on what this tool surfaces. Built for local service businesses, used by HVAC, plumbing, electrical, cleaning, lawn care, and 40+ other trades.
Payment Links + Invoicing
Send invoices with click-to-pay link. Customer pays online instantly via card or ACH, no late fees needed for most.
Learn moreWorkflow Automation
Auto-send polite-then-firm reminders at 5/15/25 days past due. Apply late fee at day 30 with one click.
Learn moreStripe Payments
Save card on file at time of service. Auto-charge on net-30 if customer doesn't pay manually. Late fees become moot.
Learn moreFrequently asked questions
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