Payment Schedule Calculator

Enter the project value and how you want it staged. Each stage comes back with an amount, an invoice date and a due date — and the amounts reconcile to the project value to the penny, which is the part that usually goes wrong when this is done by hand.

What this tool does

Staged billing exists because neither side wants to carry the whole risk. A deposit covers what the supplier spends before work starts, milestones keep cash moving through a long engagement, and a final payment leaves the customer some leverage until delivery. Choosing the split is a commercial decision; turning it into dated documents is arithmetic, and arithmetic is where it fails.

That arithmetic has one hard requirement: the stages must sum to the project value exactly. A three-way split of £10,000 computed stage by stage at 33.33% lands at £9,999 — small enough to look like nothing and large enough that a client checking the schedule against the contract finds it. Amounts here are allocated rather than multiplied, so the remainder lands somewhere deliberate and the total is exact by construction.

How it works

  1. Set the value and the shape

    Choose a deposit share, how many milestones sit in the middle, and what is held back for the final payment. The shares must total 100 — when they do not, the shortfall is named and the schedule is refused rather than quietly absorbing the difference.

  2. Amounts are allocated, not multiplied

    Each stage takes its share by allocation, so the parts always add back to the whole. The odd penny goes to whichever stage was cut hardest by rounding rather than always landing on the last one.

  3. Dates come from the project window

    The deposit is issued on the schedule date and the final invoice on completion, with milestones spread evenly between them. Given no completion date, milestones fall on 30-day spacing — a stated convention rather than a guess dressed up as an answer.

  4. Every stage gets its own due date

    A payment term is applied per stage, so the schedule shows both when each invoice goes out and when the money is actually expected. Those two columns are what turn a split into a cash-flow forecast.

Worked example

A £24,000 rebrand billed as a 30% deposit, two milestones and a 20% final payment, starting 1 September 2026 and completing 30 November 2026.

Inputs

Project value
£24,000.00
Deposit
30%
Milestones
2
Final payment
20%

Result

Deposit invoice
£7,200.00
Milestone 1
£6,000.00
Milestone 2
£6,000.00
Final invoice
£4,800.00
Total scheduled
£24,000.00

Why it matters: The two milestones divide the 50% left in the middle rather than taking an arbitrary share, and the four stages add to exactly £24,000. That last property is the one to insist on: a schedule sent to a client is checked against the contract total first, and a penny out invites scrutiny of everything else on the page.

Best practices

  • Put the schedule in the contract, with amounts and trigger points, before any work starts. A stage nobody agreed to is a conversation, not an invoice.
  • Tie milestones to deliverables rather than dates wherever you can. "On approval of the design" survives a slipped timeline; "on 15 October" does not, particularly when the client caused the slip.
  • Size the deposit to cover what you spend before the first milestone lands. A 10% deposit on a project with two months of upfront work is a loan you never agreed to make.
  • Issue each stage as its own numbered invoice rather than one document with a payment plan attached. Separate invoices age separately, chase separately and reconcile separately.
  • Keep the final stage worth something. A 5% closing payment is not worth chasing, which removes the entire incentive the final stage exists to create.

Common mistakes

Shares that do not total 100

A 30/30/30 split leaves a tenth of the project unbilled, and it is usually discovered when the final invoice is raised and the total refuses to match the contract. Better to be stopped at the schedule with the shortfall named than to find it at the end of the job.

Rounding each stage on its own

Three equal stages on £10,000 computed as value × 33.33% come to £9,999. The pound is trivial; the credibility is not, because the client compares the sum of the stages against the agreed figure and finds a discrepancy nobody can explain.

Dating the stages and then ignoring the project

A schedule that says the second milestone falls in October, on a project that slipped in August, produces an invoice the client disputes on arrival. Re-date the remaining stages when the work moves rather than issuing against a plan that no longer describes anything.

Treating a deposit as earned the moment it arrives

Money taken for work not yet performed is normally a liability until the work is done, not income in the month it lands. Exactly when it becomes revenue depends on your accounting basis and what the contract says — worth settling before it distorts a quarter you then have to restate.

Frequently asked questions

What is a normal deposit on project work?

25% to 50% is common in creative and construction work, and higher where the supplier commits to materials or subcontractors before starting. The right figure covers what you spend before the first milestone is billed; anything below that means you are financing the client.

How many milestones should a project have?

Enough that no gap between payments is longer than you can comfortably fund. Monthly suits a three-month engagement; a single midpoint stage is plenty on a six-week one. Each extra stage is another document to raise, send and chase, so more is not automatically better.

Should each stage be its own invoice?

Yes. Each stage is a separate document with its own number, issue date and due date, and frequently its own tax point. A single invoice with a payment plan attached is harder to age, harder to chase, and awkward to reconcile when one stage has been paid and another has not.

What happens when the scope changes mid-project?

Re-schedule the stages that have not been invoiced yet, and raise the change as its own stage or its own document. Adjusting stages already issued breaks the link between the schedule and the contract it was built from.

Can I use this for a monthly retainer?

No — a retainer is the same amount repeating on a calendar, which is a different shape with no total to reconcile against. The recurring invoice schedule builder covers that. Use this one when a single agreed value is being divided into parts.

Do the stages have to be equal?

No, and usually they should not be. Weight them towards where the work actually sits: a stage covering a month of build belongs above one covering a week of revisions, and an even split across uneven work is what leaves you funding the expensive part.

Turn the answer into an invoice

The result above transfers straight into the invoice generator — dates, amounts and terms already filled in. Free, no account needed.

Open the invoice generator

Sources & further reading

Related

Invoice types

Published · General information, not legal, tax or financial advice.