Milestone and progress billing — how project billing really works

Why project billing is not product billing

A trader bills a product: pick the item, quantity, rate, done. A project business bills work — the progress of a deliverable over weeks or months, in stages, each of which has to be justified to a customer who is watching. One order (the contract) produces a whole series of bills: perhaps an advance, then running-account bills as work proceeds, then a final bill after handover. There is no dispatch to invoice against and no single “sale” to raise, which is exactly why generic invoicing tools struggle with it.

The structural answer is to bill against the project and its tasks. Because project bills are resource-itemised and keyed to tasks, the same data that planned and executed the work can be sliced to bill it — rather than re-typing amounts into a separate invoice. That is what makes progress and running-account billing possible without a parallel spreadsheet, and it is the subject of the pillar guide on what project management software is.

Three ways to bill one project

Because the bill is built from resource-itemised, task-keyed data, one project can be billed several different ways — and often is, at different points in its life.

Whatever the basis, the mechanics are identical: the bill references the project, draws its lines from the tasks and their resources — each with a resource group, quantity, unit, rate and amount — applies charges, and prints as a compliant bill. Because every bill hangs off the same project record, the system always knows cumulative billed value against contract value, which is the number that stops you over-billing a project or leaving earned work unbilled. See Project & Milestone Billing for how the bill is built.

RA and progress bills, keyed to tasks

The working document of long-cycle project billing is the running-account (RA) bill: a periodic bill for work executed since the last one, presented cumulatively. RA bill 4 says: total work done to date, minus what RA bills 1–3 already billed, equals this bill. It is the pattern construction and EPC firms live by, but the same idea — bill the progress, not the whole — applies to any milestone-billed project.

What makes an RA or progress bill defensible is that its lines are keyed to the tasks the work was planned and executed against. A bill line is not a round number a manager felt was fair; it is the resource consumed on a specific task, at the rate the estimate used. That is only possible when billing shares the same task-keyed data as planning and execution — the through-line from a Bill of Resources to a bill.

Retention, advances and subcontractors

Between the gross value of a project bill and the money that reaches your bank sits a stack of adjustments, and each must be recorded against the bill rather than remembered.

Retention money. The customer holds back a percentage — commonly 5–10% — from each certified bill as security until the defect-liability period ends. Retention is earned revenue you have billed but cannot collect yet, so it must be tracked per project and per bill; contractors who leave it in spreadsheets routinely forget to claim lakhs of it years after handover.

Mobilisation advances. An advance paid up front is recovered proportionately from each progress bill, so every bill must show the recovery and the running balance.

Subcontractor bill passing. On the buy side, subcontractor bills are passed and cleared against their purchase order on the same engine — so what you owe a subcontractor and what you bill your customer for the same work are visible together, not argued over on email. In India this billing rides on GST works-contract rules and RA-bill conventions; treatment varies by contract, so confirm the specifics with your CA.

What makes a claim defensible

Every project claim is, in the end, an argument you may have to win: we have earned this much, here is why. The claim is defensible only when the bill is built from the plan — when each line traces back to the task and the resource behind it, and the cumulative total can be checked against the contract. A bill assembled separately, in an invoicing tool that never saw the project plan, cannot make that trace, which is why disputed bills so often come from disconnected billing.

The other half of defensibility is the estimated-versus-actual record behind the bill. When you can show the customer that the resources billed are the resources planned and consumed — with progress %, dated logs and material issued all keyed to the same tasks — the conversation is short. When you cannot, every RA bill becomes a negotiation.

How Fast Project Software bills projects

Fast Project Software raises a project bill as a header — bill number, date, project and party — with resource-itemised lines by task and resource group, each carrying quantity, unit, rate and amount, so a project can be billed by project, by resource or by milestone from one structure. Because the bill draws on the same task-keyed Bill of Resources data that planned and executed the work, progress and RA bills trace straight back to the tasks behind them, retention can be held per contract, and subcontractor bills are passed and cleared against a purchase order. Bills print as a compliant document and post alongside the platform’s invoicing through Fast Billing & Accounts, drawing on the same party master. It suits construction, EPC, ETO and fabrication firms; pricing is indicative and in INR — see pricing and confirm GST treatment of your contracts with your CA.

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