Progress Billing Explained: Invoicing for Long-Term Projects

Progress billing means invoicing as work advances rather than waiting until the end. Software implementations, consulting programs, agency retainers with a defined build, engineering studies and construction all use it, so the supplier is not financing months of labor while the client spreads the cost across the project.

The method is the same in every industry: split the contract price into lines (a schedule of values), estimate how much of each line is done at the end of each period, and bill the increase since the last invoice. Construction adds formal pay-application forms, retainage and lien waivers; those are covered in the construction invoicing guide. If your project divides into a few checkable deliverables instead, milestone-based invoicing is usually simpler.

Models of progress billing

Percent-complete draws

Invoice each period, usually monthly, for the share of each schedule-of-values line completed so far. This is the classic construction model, and it works just as well for a software rollout or a research program.

Fixed installments

Bill an agreed amount each period until the contract is fully billed. Simpler, but it can drift away from the work actually done, so say in the contract how the schedule adjusts if the work slips.

Milestone-linked progress

Each invoice ties to a defined deliverable rather than a percentage. Once every invoice is tied to an event, this is really milestone invoicing, which bills fixed amounts at fixed gates.

Cost-plus with caps

Less common outside certain consulting niches. It needs transparent expense backup and strong trust.

Worked example: month two of a $48,000 software implementation

Illustrative figures. A consultancy implements a CRM for a fixed $48,000, billed monthly on percent complete with no retainage. The schedule of values has four lines. In month one it billed discovery in full ($6,000) and 10% of configuration ($1,800), $7,800 in total. At the end of month two:

Check: $7,200 + $3,000 = $10,200, and $18,000 - $7,800 = $10,200. Balance left to bill: $48,000 - $18,000 = $30,000. The client's project lead signs off the percentages before the invoice goes out, so accounts payable has nothing to query.

Worked example: the same method with retainage

Retainage is common in construction and rare elsewhere. A contractor has a $60,000 contract with 5% retainage. In month one, work completed was $15,000, billed at $15,000 less 5% retainage = $14,250, and paid. By the end of month two, work completed to date is $27,000 (45% of the contract).

Check: $27,000 - $1,350 - $14,250 = $11,400. Balance left to bill: $60,000 - $27,000 = $33,000, plus the $1,350 retainage, which is released on the final invoice when the contract says. The construction invoicing guide covers retainage release and lien waivers.

When progress billing fits

• Long projects with measurable work, such as implementations, engineering studies or construction, where you would otherwise finance months of costs.
• Use milestone billing instead when the work divides into a few checkable deliverables (milestone invoicing).
• Use a fixed price on completion for short jobs, and hourly billing when scope is open-ended (hourly vs fixed-price invoicing).
• Use a retainer for ongoing capacity rather than a defined project (retainer invoicing).

Setting up progress billing step by step

Step 1: Agree a schedule of values before kickoff

Break the contract price into lines the client can check, for example discovery, configuration, migration and training, or demolition, framing, electrical and finishes. Each line has a value, and the lines must add up to the contract price.

Step 2: Agree how progress is measured and when you bill

Write into the contract who confirms percent complete (your judgment, joint sign-off or an architect's certification), the billing date each month, the payment terms, whether retainage applies and when it is released, and your stop-work rights if payments run late (see payment terms). If you take a deposit, check any legal cap for your trade first.

Some places regulate these clauses. On California home improvement contracts, the Contractors State License Board requires a payment schedule headed "Schedule of Progress Payments" and says payments may not run ahead of the work done or materials delivered. On US federal construction contracts, retainage is limited to a maximum of 10% and is meant for unsatisfactory progress (FAR 32.103).

Step 3: Bill each period from the schedule

Each invoice shows contract value, change orders, work completed to date, retainage, previous billings and the amount due now. Transparency prevents "I thought we already paid that" disputes.

Step 4: Bill change orders as their own lines

Get written approval (an email reply can be enough if your contract allows it) before doing extra work, then add it to the schedule as a separate line so the original contract value stays visible. Invoicing scope creep covers the wording.

Step 5: Close with a final invoice

The final invoice bills the remaining work and any retainage release, lists every earlier invoice and payment, and states the balance that closes the account. See the final invoice template.

What to show on each progress invoice

• Contract value and approved change orders
• Work completed to date, line by line if you use a schedule of values
• Retainage held to date, if any
• Previous billings and this period's amount
• Balance remaining to bill
• Brief narrative of work performed in the period
• Taxes consistent with invoice tax compliance

If you also took a deposit, show how it is credited against progress or final billing. The progress invoice template lays out these columns.

How to keep percent-complete billing honest

Percent complete is an estimate, and optimism inflates it. A few habits keep the numbers defensible:

• Tie each increase to evidence: a staging link, test results, photos, an inspection report or the client's written sign-off.
• Never bill past the contract total, even if the work feels ahead. Unbilled change orders go through Step 4 first.
• Correct errors openly. If a prior period was over-billed, issue a credit note or show the adjustment on the next invoice, never silently.
• Compare cumulative billing with cash collected each month. A growing gap usually means accounts payable friction, so chase it with payment reminders and a follow-up strategy before one late payment compounds across months. Show any unpaid earlier invoice on the next one.
• Track retainage outstanding if it applies. It is money you have earned but not received.
• Keep the paper trail together. Progress billing creates more documents than a single final bill, so keep the schedule, sign-offs and invoices in one audit trail, and ask your accountant how to record revenue on long contracts.

Progress billing in InvoiceQuickly

InvoiceQuickly has no progress-billing, schedule-of-values or retainage feature, and line prices cannot be negative. You can still send progress invoices:

• Bill each schedule line at the net amount due this period, with the gross amount and any retainage written in the line description.
• Put the full running schedule in the notes, which hold up to 5,000 characters and print on the PDF.
• Duplicate last period's invoice and update the figures each month.
• On Pro, track time and expenses against a project and bill them into a draft invoice when part of the work is billed by the hour, and issue a credit note against an invoice if a period was over-billed.

Frequently asked questions

What is the difference between progress billing and milestone billing?

Progress billing bills whatever share of the work was completed in the period, usually monthly, against a schedule of values. Milestone billing bills a fixed share of the contract when a defined event happens, such as an approved prototype.

How do I calculate a progress billing amount?

Add up work completed to date, subtract retainage on that total if the contract has it, then subtract what you billed in earlier periods. In the software example above: $18,000 - $7,800 = $10,200. In the retainage example: $27,000 - $1,350 - $14,250 = $11,400.

What is retainage?

A percentage of each progress payment that the client holds back until the work is complete, to protect against defects or unfinished work. The contract sets the rate and the release terms; on US federal contracts it may not exceed 10%.

How do I handle scope creep mid-project?

Price it as a change order, get written approval before starting, and add it as its own line on the next progress invoice, for example "Change order 2, additional landing page, approved 12 April, $1,200". Don't absorb extra scope silently.

Can I do progress billing as a sole proprietor?

Yes. Progress billing is a billing method, not a legal structure. The documentation (contract, schedule of values, change orders) is the same whatever your business entity.

What if the project runs over budget?

On a fixed-price contract, cost overruns are yours unless the scope changed. If the client asked for extras, bill a change order. If something neither side could have anticipated came up, renegotiate the remaining schedule in writing before you bill it.

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Bill long engagements as you earn, not only when you finish. Get started with InvoiceQuickly.

This article is general information, not legal or tax advice. Last reviewed 4 November 2026.