Late Fee Calculator for Contractors
Construction is the industry where late payment is structural rather than accidental. Money moves down a chain from owner to general contractor to subcontractor to supplier, and every link holds it a little longer. Add retainage withheld until closeout and a progress-billing cycle that can stretch a 30-day term into 75 days in practice, and interest on overdue invoices stops being a nicety.
Use the calculator for the figure, but read the section below first. Contractors have two levers that most trades do not: statutory prompt-payment interest, which may entitle you to a rate set by law rather than by your contract, and mechanic's lien rights, which are a far stronger form of pressure than any late fee.
Days your terms allow before fees start.
1.5% per month is the common business default.
Late fee
$840.00
Accrued over 35 chargeable days.
- Original balance
- $48,000.00
- Total now due
- $48,840.00
- Cost per additional day
- $24.00
- Effective annual rate
- 18%
Quote this to show the client what waiting costs them.
Late fees are only enforceable if they appear in terms your client agreed to, and maximum rates are capped by local usury law. This is an estimate, not legal advice.
Starting values are set for a typical contractors scenario — change any field to match yours. Need the plain version? Invoice Late Fee Calculator.
Prompt-payment statutes may set your rate for you
Most US states, and the federal government for its own contracts, have prompt-payment legislation covering construction. These laws set deadlines for paying contractors and subcontractors, and specify the interest that applies when the deadline is missed. Where they apply, the statutory rate can exceed what your contract says, and the entitlement does not depend on having a late-fee clause at all.
The details vary substantially by state and by whether the project is public or private, so treat this as a prompt to check rather than an answer. The practical point is that a contractor chasing an overdue payment should establish which regime applies before quoting a rate — you may be entitled to more than the 1.5% in your terms.
- Public projects usually have shorter statutory deadlines and clearer interest entitlements than private ones.
- Federal work falls under the Prompt Payment Act, with interest set by a published Treasury rate.
- Many statutes let you recover attorney's fees from the non-paying party, which changes the economics of pursuing the debt.
- Pay-when-paid clauses are limited or unenforceable in some states — a general contractor cannot always defer your payment indefinitely because the owner has not paid.
Retainage is not the same as an overdue invoice
Retainage — typically 5% to 10% withheld from each payment until the project closes out — is contractually withheld, not late. Charging interest on it while the contract still permits it to be held will undermine your position on the amounts that genuinely are overdue.
The moment retainage becomes collectable is defined by your contract and often by statute: substantial completion, final acceptance, or a fixed period after closeout. Once that trigger passes, unreleased retainage is an overdue balance like any other, and it is frequently the largest one you are owed. Calculate it separately from your progress billings so that both figures are defensible.
The escalation ladder in construction
| Step | Lever | Why it works |
|---|---|---|
| 1 | Statement showing accrued interest | Creates a documented, growing balance |
| 2 | Preliminary notice / notice of intent to lien | Signals the next step without filing |
| 3 | Stop-work notice where permitted | Halts progress the owner needs |
| 4 | Mechanic's lien filing | Clouds title and blocks refinancing or sale |
| 5 | Bond claim on a bonded project | Reaches the surety rather than the debtor |
Frequently asked questions
- How much interest can a contractor charge on a late payment?
- Whichever is higher of your contract rate and any applicable statutory prompt-payment rate, subject to the usury cap in your state. Contract rates of 1% to 1.5% per month are common in construction, but on public work the statutory rate may be more favourable, so check before you invoice for interest.
- Can I charge interest on withheld retainage?
- Not while the contract permits it to be held. Once the contractual or statutory release trigger has passed — substantial completion, final acceptance, or a set period after closeout — unreleased retainage becomes an overdue balance and interest can accrue on it. Track it as a separate line from your progress billings.
- Is a late fee more effective than filing a lien?
- No. A lien clouds title and stops the owner refinancing or selling, which is a far stronger form of pressure than interest. The practical sequence is to let interest accrue and document it while you work through notice requirements, keeping the lien as the real lever. Watch the filing deadlines closely — they are unforgiving.
- What if the general contractor says they cannot pay until the owner pays them?
- That is a pay-when-paid or pay-if-paid clause, and its enforceability varies by state — some limit it, some void it outright for subcontractors. Even where it holds, it typically defers payment rather than eliminating the obligation. Check your state's position before accepting an indefinite wait.
- Should the interest clause be in my bid or my contract?
- Both. Put it in the bid so it is never a surprise, and in the executed subcontract so it is enforceable. Repeat it on every progress invoice. Contractors who only raise interest after a payment goes late usually end up negotiating it away.