Slow-paying customers are costing you more than you think. Calculate the true cost of late invoices—interest loss, collection time, cash flow gap—and see what late fees and net terms actually need to look like to run a healthy trade business.
A $4,500 invoice sitting unpaid for 45 days isn't just costing you $18 in interest. It's the payroll you floated while waiting, the credit line you drew on, the 2 hours of follow-up time that could have been billable work, and the mental overhead of chasing money you already earned. When you calculate all of it, a chronic late-payer who averages Net 60 on Net 30 invoices is costing you 3–5% of their invoice value in real costs. That's your entire margin on a low-margin job—gone before you deposit the check.
A late fee you add after the fact is unenforceable in most states. A late fee stated clearly in your service agreement, proposal, and invoice—typically "1.5% per month on balances over 30 days"—is enforceable and serves two purposes: it compensates you for the cost of waiting, and it changes the customer's behavior. Customers who know there's a fee pay faster. The fee doesn't need to be punitive—1.5%/month (18% APR) is standard and legally defensible in most jurisdictions. Put it in every document they sign.
Chasing individual late invoices is a symptom, not the problem. The problem is a billing system that doesn't create urgency. Solutions that work: require a deposit before starting work (30–50%), invoice the same day the job closes (not at end of month), send automated reminders at 7 days overdue and 14 days overdue, and offer a 2% early-payment discount for payment within 10 days. A business that collects 95% of invoices within 30 days has dramatically better cash flow than one with 30% of revenue aging past 60 days.
The Tradesman's Business Starter Kit includes a service agreement with late fee language, financial tracking forms, and the payment terms template that gets trade contractors paid faster. Guide from $19 — Complete Kit with all 19 templates, $49.
Get the Business Kit — $19Slow-paying clients aren't just annoying — they cost you money. This calculator figures out the real cost of a late invoice: the interest expense on money you're owed, the time value of capital tied up in receivables, and what you'd need to charge in late fees to break even. Use it to set your late payment policy and decide when it's worth pushing back.