Overdue Invoice Sheet
Interest on the original sum, for the days past the DUE date. And only if the terms said so.
BFCBrilliance · bfcbrilliance.com/tools/invoice-late-fee-calculator
The arithmetic
- INTEREST
- invoice x annual rate x days ÷ days in year
- DAILY RATE
- invoice x annual rate ÷ days in year
- 1.5% a month
- = 18% a year
- 2% a month
- = 24% a year
- 18% compounded monthly
- = about 19.6% effective
- 360-day basis
- yields about 1.4% more than 365
- ⚠ Late starts
- at the DUE date, not the invoice date
- ⚠ No prior agreement
- generally no enforceable fee
- ⚠ Waiving it? Say so
- an unmentioned clause is not a clause
Overdue ledger
| Client | Invoice | Due date | Days late | Interest | Chased? |
|---|---|---|---|---|---|
This invoice
- Client
- Invoice number
- Amount
- Invoice date
- Terms
- DUE DATE
- Days late
- Rate in terms
- INTEREST
- Daily accrual
- Fixed fee
- TOTAL OWED
- Reminder 1 sent
- Reminder 2 sent
- Decision
Before charging interest
- Rate was in terms the client ACCEPTED, before the work
- Counted from the DUE date, not the invoice date
- Day-count basis matches the contract
- Checked whether a statutory right or cap applies where you are
- Simple vs compound matches what the terms actually say
- Polite reminder sent first, citing the clause
- Relationship value weighed against the sum
- Any waiver stated EXPLICITLY rather than left silent
- Significant sums taken to a qualified adviser
The clause has to exist first
Interest is a contractual term, not something you can add to a reminder after the fact. It needs to be in what the client accepted — engagement letter, purchase order, signed quote, or standard terms referenced on the invoice. A rate that first appears while chasing is generally unenforceable, and it makes a reasonable request look opportunistic, which costs more than the interest.
Quote it annually to yourself
Terms are written monthly because 1.5% sounds small. It is 18% a year, and about 19.6% effective if it compounds. Convert before you set it — both so the figure is defensible if challenged, and so you know what you are actually asking for.