Project Invoice Calculator
Invoice fixed-price or milestone project work with expenses, discounts, tax, and deposits.
How is project invoice calculator worked out?
A project invoice bills either the whole fixed fee or the percentage of it represented by the milestone reached, plus reimbursable expenses and tax, less any deposit already taken.
Project Invoice Calculator
Balance due
$6,000.00
- Invoice total
- $6,000.00
- Fee remaining after this stage
- $6,000.00
- Still to be invoiced on later milestones.
Show the working
| Milestone at 50% of project fee | $6,000.00 |
| Reimbursable expenses | $0.00 |
| Subtotal | $6,000.00 |
| Discount | -$0.00 |
| Tax | $0.00 |
| Invoice total | $6,000.00 |
| Less deposit applied | -$0.00 |
| Balance due | $6,000.00 |
Fixed-price work is invoiced against milestones rather than effort, which means the only number that matters is the percentage of the agreed fee that the completed stage represents. Getting that percentage from the contract rather than from a sense of how much work is done is what keeps milestone invoicing uncontroversial.
The formula
Milestone fee = total project fee × milestone %
Subtotal = milestone fee + reimbursable expenses
Discount = subtotal × discount %
Tax = (subtotal − discount) × tax rate
Invoice total = subtotal − discount + tax
Balance due = invoice total − deposit applied to this stageSet the milestone to 100% for a single fixed-price invoice at completion. Where a deposit was taken up front, apply it against the stage your contract says it covers rather than spreading it across every invoice — spreading it makes each invoice harder to reconcile against the contract.
Choosing milestones that get paid
The best milestones are events the client can observe without your help: a delivered document, a launched page, a signed-off design. Milestones defined by internal effort — "development 60% complete" — put you in the position of asserting progress the client cannot verify, which is where payment stalls. Tie each stage to a deliverable in the contract and invoice the moment it lands.
Scope changes on fixed-price work
A fixed price is fixed against a defined scope, so anything outside it belongs on its own line with its own approval, not absorbed into the next milestone. Absorbing changes quietly is how a profitable fixed-price project becomes an unprofitable one, and because the invoice total never changed, nobody notices until the project is finished.
Frequently asked questions
How do I invoice for a project milestone?
Multiply the total agreed project fee by the percentage that milestone represents in your contract, add any reimbursable expenses, apply tax, and deduct any deposit allocated to that stage. Name the milestone in the line description exactly as the contract names it.
Should I take a deposit on a fixed-price project?
A deposit is normal on project work and does two useful things: it covers your early costs and it confirms the client is committed. Invoice it separately before starting, then apply it against the stage your contract allocates it to rather than spreading it across all invoices.
How many milestones should a project have?
Enough that you are never carrying more unpaid work than you can afford to lose. For short projects, a deposit and a completion payment is usually enough; for longer engagements, a stage every few weeks keeps cash arriving during the work rather than months after it.
Put the number on an invoice
The free invoice generator builds the document around your figures — line items, tax, payment terms — and downloads a print-ready PDF. No signup required.
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