A late fee is an extra charge you add to an invoice when a client misses its due date. It’s usually either a flat amount (say, $25) or a percentage of the unpaid balance, and it’s meant to nudge clients toward paying on time.
Flat fee vs. percentage
There are two common ways to structure a late fee, and the right one depends on the size of your invoices.
- Flat fee — a fixed dollar amount, like $25 or $50, no matter how large the invoice is. Simple to explain and predictable for the client. Great for smaller, consistent invoices.
- Percentage fee — a percent of the outstanding balance, often charged per month it stays unpaid (for example, 1.5% per month). This scales with the invoice, so a big overdue balance carries a bigger consequence.
Whichever you pick, the golden rule is the same: the client should know about it before the invoice is overdue. Spell it out in your payment terms so it never feels like a surprise.
When a late fee applies
A late fee only kicks in once an invoice passes its due date and is still unpaid. That due date comes from your payment terms — Net 15, Net 30, due on receipt, and so on. Until that date arrives, there’s nothing late about the invoice, so there’s no fee to add.
Many freelancers also build in a short grace period (a few days) before applying anything, and they send a friendly reminder first. A late fee works best as a gentle backstop, not a gotcha.
Tip: Late fees and what’s enforceable can vary by location and by what’s written in your agreement. When in doubt, keep your terms reasonable and run anything formal past an accountant or lawyer.
A real-world example
You send a $1,200 invoice with Net 15 terms and a note: “A 1.5% monthly late fee applies to overdue balances.” Day 15 passes with no payment. You send a reminder. A week later it’s still unpaid, so you add a $18 surcharge line (1.5% of $1,200), label it clearly, and resend. The client pays the next day — the small charge did its job.
How Fee-Lion handles it
Fee-Lion doesn’t auto-stack penalties, which keeps you in control of the client relationship. Instead, you add a late fee as a surcharge line on the invoice, the same way you’d add discounts or surcharges on an estimate.
- Open the overdue invoice from Invoices in the left sidebar (its status will read Overdue).
- Add a surcharge line — give it a clear label like “Late fee (1.5%)” and enter the flat amount or the calculated percentage.
- Save, then use the invoice’s reminder action to send a payment reminder so the client sees the updated total and the Pay button right away.
To make sure clients are never caught off guard, set your expectations up front under Settings → Preferences. Your default payment terms drive each invoice’s due date, and you can mention your late-fee policy there so it travels with every estimate and invoice you send. When the client opens their no-login portal link, they’ll see the revised invoice — surcharge included — and can pay by card in one click.
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