Milestone & Progress Billing Guide
Waiting until project completion to invoice is a cash-flow trap on long jobs. Milestone billing breaks the project into payable stages, so money arrives as work progresses. Here is how to define milestones and invoice them without friction.
Defining Billable Milestones
A good milestone is objective and verifiable: 'design approved', 'beta delivered', 'foundation poured' — not 'phase 1 mostly done'. Each milestone should represent roughly equal value slices of the project (common splits: 30/30/40 or 25/25/25/25). Define them in the contract with acceptance criteria so 'done' is never a matter of opinion.
Tie payments to client actions where possible. A milestone like 'client approves designs' puts the ball in their court with a deadline — add a clause that approval is deemed given after a set number of days without feedback, or one slow reviewer can stall your cash flow.
Invoicing Each Milestone
Invoice promptly when a milestone is accepted — same day or next day. Reference the contract, the milestone name, and the acceptance date: 'Milestone 2 of 4 — Development complete, accepted [date] per agreement dated [date]'. Show the running total: contract value, previously invoiced, this invoice, remaining balance.
Keep milestone invoices in your normal sequential numbering; do not create a separate sequence. The running-total format lets any client (or auditor) reconstruct the project finances from the invoices alone.
Progress Billing for Ongoing Work
On construction and long service contracts, progress billing invoices a percentage of completion each period (often monthly) rather than discrete milestones. Base it on measurable progress — an architect's certification, or costs incurred versus budget — and document the calculation on or with the invoice.
Retainage is common in construction: the client holds back 5-10% of each progress payment until final completion. Invoice the gross amount, show the retainage held, and track the retained balance carefully — it is your money, just delayed, and it needs its own final invoice at project close.
Handling Milestone Disputes
Disputes usually mean the acceptance criteria were vague. When a client rejects a milestone, get the specific objections in writing, fix what is legitimately wrong, and re-submit promptly. For subjective rejections, refer back to the agreed criteria — that is what they are for.
Protect yourself with a stop-work clause: if a milestone invoice goes unpaid beyond the agreed terms, work pauses until payment. Enforcing this once teaches clients that milestones are real deadlines, not suggestions.
Frequently asked questions
How many milestones should a project have?
Enough that no single payment exceeds what you can comfortably float — typically 3-5 for projects spanning 1-6 months. Very long projects suit monthly progress billing instead of a few giant milestones.
Should the first milestone be a deposit?
Yes, in most cases. A kickoff payment of 20-50% on signing covers mobilization costs and confirms commitment. Label it clearly as Milestone 1 / deposit in the contract and invoice.
What is retainage in progress billing?
A percentage (often 5-10%) the client withholds from each progress payment until the project is fully complete and accepted. It protects the client against unfinished work; you invoice the retained amount at final completion.
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