How to Write a Final Invoice for a Construction Project (Without Losing Your Lien Rights)
How do you write a final invoice for a construction project? The invoice part is easy: total contract amount, less what you already billed, plus change orders, less retainage already withheld, plus the retainage you are now releasing. The part that costs contractors real money is what goes in the envelope with it: the lien waiver.
Sign the wrong one at the wrong time and you have traded your security interest for a promise. A final invoice has a different job from a progress invoice. A progress invoice asks for this month's money and carries a waiver for this month's work. A final invoice asks for everything left, including the retainage the owner has been holding since day one, and it closes out your lien rights on the project. Because it closes things out, the paperwork around it matters more than the arithmetic.
What the invoice itself needs
The contract total, including every approved change order, listed separately so the owner can reconcile it against their records. Every prior payment, with invoice numbers and dates. The retainage withheld to date and the retainage now due for release. Any credits or backcharges, stated plainly rather than buried in a net figure. And the balance due, labeled FINAL, with payment terms and the project name and address matching the contract exactly. Owners reject final invoices for administrative mistakes more than for disputes: the project name does not match, a change order number is missing, the retainage math does not foot. Check the arithmetic twice and the names once.
The lien waiver is where the danger lives
There are four types, and the only question that matters is which one you are signing and when. A conditional waiver on final payment says your lien rights end when the payment clears. That is the one you attach to the final invoice before you have been paid. An unconditional waiver on final payment says your lien rights are gone, period, effective the moment you sign. That one gets signed only after the money is in your account and cleared, never before. Signing an unconditional waiver to "speed things up" while the check is in the mail is how contractors end up with no payment and no lien. The waiver is the owner's security. The conditional version keeps yours intact until the cash lands.
Two details people get wrong. First, exceptions. If anything is disputed, an unpaid change order, a backcharge you do not accept, write it into the exceptions section of the waiver. A waiver with no exceptions releases everything. Second, lower tiers. General contractors will ask for lien waivers from your subcontractors and suppliers before releasing your final payment. Collect them before you submit, or your final invoice will sit in someone's inbox while you chase paperwork downstream.
The retainage piece
And the retainage piece, since that is usually the largest line on the final invoice. Retainage is the percentage, commonly 5 to 10 percent, the owner holds back from every progress payment as security for completion. The final invoice is how you ask for it back. Some contracts release it at substantial completion, some at final completion, some in two halves. Read your contract's release trigger before you invoice for it, because billing retainage before the trigger is the fastest way to get the whole invoice kicked back.
My opinion, stated plainly: send the final invoice with a conditional waiver attached, keep a copy of everything, and sign nothing unconditional until the funds clear. The arithmetic is rarely what burns contractors at closeout. The signature is.
Frequently asked questions
What should a final construction invoice include?
The full contract total with approved change orders listed separately, all prior payments with invoice numbers and dates, retainage withheld and now due, any credits or backcharges, and the balance due labeled FINAL. Match the project name and address to the contract exactly.
Should I sign a lien waiver before I get paid?
Only a conditional waiver. A conditional waiver on final payment releases your lien rights when the payment clears, so it is safe to send with the final invoice. Never sign an unconditional waiver before the funds are in your account and cleared.
What is the difference between a conditional and unconditional final lien waiver?
A conditional final waiver is void if you are not paid; it takes effect only when payment clears. An unconditional final waiver releases your lien rights the moment you sign, whether or not you have been paid. Use conditional with the invoice, unconditional after the money clears.
When is retainage released on a construction project?
It depends on the contract: commonly at substantial completion or final completion, sometimes in two halves. Check your contract's release trigger before billing for retainage, because invoicing it early gets the whole invoice rejected.
What if part of the final amount is disputed?
List the disputed items in the exceptions section of the lien waiver. A waiver with no exceptions releases all claims. Carve out the disputed change order or backcharge in writing so you keep your rights on that portion.
Related reading: Progress Invoices Explained · What Is Retainage on a Contractor Invoice? · The Contractor Invoice That Gets Paid Faster · How Long Do You Have to File a Mechanics Lien? · How to Invoice Change Orders