An interim payment is a partial payment made during an ongoing contract, based on work already performed, so the contractor or vendor can cover payroll, materials, and overhead before the job is complete. These payments are the norm on construction projects, federal procurement contracts, long software builds, and professional service engagements that stretch across months. The payment amount is tied to verified progress, so the money moving each cycle reflects what has actually been earned, not a guess.
In U.S. legal and business usage, “interim payment” almost always refers to this kind of progress billing. The term is also used in United Kingdom litigation to describe an advance paid to a claimant before a case concludes, but that meaning is uncommon in American practice.
Where Interim Payments Are Used
Construction is the setting most people picture. A general contractor building a hospital or a bridge has to pay subs, suppliers, and crews every month, and waiting for one lump sum at completion would sink the firm. Monthly progress payments reimburse work already in place and keep the project moving.
Federal procurement is the other big arena. The government makes progress payments on both construction contracts and manufacturing contracts for specialized equipment with long production timelines. On manufacturing contracts, federal regulations allow monthly progress payments computed at 80 percent of the contractor’s incurred costs, with the total capped at 80 percent of the contract price. Subcontractors whose work involves at least six months of lead time before the first delivery can have their financing costs folded in as well.1Acquisition.gov. FAR 52.232-16 Progress Payments On fixed-price construction contracts, the government makes monthly progress payments based on approved estimates of work completed.2Acquisition.gov. FAR 52.232-5 Payments Under Fixed-Price Construction Contracts
The same concept shows up elsewhere. Software firms working under milestone-based contracts bill as each module is delivered. Engineering and consulting engagements bill monthly against a total project fee.
How the Payment Amount Is Calculated
Two approaches control how much a contractor can bill at each cycle: milestone payments and progress-based measurement.
Milestone payments are the simpler version. The contract names specific deliverables and attaches a dollar amount to each. Finish the foundation pour, earn the amount tied to that milestone. Erect the structural steel, trigger the next fixed payment. The approach is clean but rigid: work that falls between milestones produces no billing, so a contractor can go weeks without invoicing.
Progress-based measurement is more common on large projects. The contractor bills each month based on the percentage of total work completed. Under current accounting standards, that measurement uses either an output method (units delivered, surveys of work performed) or an input method (costs incurred against estimated total costs). The older “percentage of completion” label still gets used casually in the field.
The Schedule of Values
On most construction contracts, the baseline for every payment request is the Schedule of Values. It breaks the total contract price into line items — sitework, concrete, structural steel, electrical, and so on — with a dollar value assigned to each. The sum of all line items equals the contract price. Each month, the contractor lists the percentage of each line item completed, multiplies by the line value, and adds them up to get the gross amount earned to date.
The industry-standard forms are the AIA G702 (Application and Certificate for Payment) and G703 (Continuation Sheet). The G703 mirrors the Schedule of Values line by line, showing previous billings, current work completed, materials stored on site, and the amount now due. The owner or architect reviews, verifies, and either approves or adjusts the amounts before authorizing payment.
Change Orders
Approved change orders adjust the contract price and roll into the next payment application. Pending or disputed change orders are trickier. Some contracts let the contractor include the undisputed portion of a pending change order; others require full approval before any billing against it. On federal contracts, the contracting officer may revise the contract price to reflect the estimated value of pending changes when computing progress payments, particularly where a loss appears likely.3Acquisition.gov. FAR Part 32 – Contract Financing On private contracts, how unapproved changes get handled is whatever the parties negotiated.
Retention: The Portion Held Back
Almost every construction contract includes a retention clause, and it is where contractors feel the squeeze. Retention is a percentage of each progress payment that the owner holds back as security. If the gross amount earned this month is $200,000 and the retention rate is 10 percent, the contractor receives $180,000. The withheld $20,000 accumulates over the life of the project and is not released until the work is substantially complete and accepted.
On federal construction contracts, the maximum retention is 10 percent of the approved amount, though the contracting officer can reduce it as the project nears completion if performance has been strong.4Acquisition.gov. FAR 32.103 Progress Payments Under Construction Contracts State laws on private projects vary. Some states cap retention at 5 percent, others allow up to 10 percent, and a few use a sliding scale that drops the percentage once the project passes the halfway mark. The trend has been toward lower caps, with a growing number of states limiting retention to 5 percent.
Retention gives the owner leverage to make sure the contractor returns to finish punch-list items and correct defects rather than walking after the last big payment. It also creates a cash flow burden. On a $10 million project with 10 percent retention, the contractor is effectively financing $1 million of the owner’s project until final acceptance. That cost rolls downhill: general contractors typically withhold retention from their subs at the same rate.
Submitting the Payment Application
The payment application is the formal request that triggers each interim payment. On private construction projects, this is typically the AIA G702/G703 package submitted monthly on a date the contract specifies. The contractor fills in work completed and materials stored for each line item, calculates total earned to date, subtracts retention and prior payments, and arrives at the current amount due.
Federal construction contracts add requirements. Along with the itemized request, the contractor must certify that the amounts are only for work performed under the contract, that all subcontractors have been paid from prior payments, and that the request does not include amounts the contractor intends to withhold from subcontractors.2Acquisition.gov. FAR 52.232-5 Payments Under Fixed-Price Construction Contracts This certification carries real weight. False statements can trigger penalties beyond just a denied payment.
Some contracts and state laws also require a notarized sworn statement listing all subcontractors and suppliers, the amounts owed each, and confirmation that prior payments were distributed properly. Submitting an incomplete or defective application resets the clock on when payment is due, so the paperwork matters as much as the numbers.
When Payment Is Due
Contractors on federal projects have a statutory safety net. The Prompt Payment Act requires federal agencies to pay construction progress payments within 14 days of receiving a proper invoice. Miss that deadline and interest accrues automatically starting the day after the due date.5Acquisition.gov. FAR 52.232-27 Prompt Payment for Construction Contracts For cost-reimbursement service contracts, the payment window is 30 days.6eCFR. 5 CFR Part 1315 Prompt Payment
The interest rate is set by the Treasury twice a year. For the first half of 2026, the rate is 4.125 percent, calculated on a 360-day year using simple daily interest.7Fiscal.Treasury.gov. Prompt Payment The agency head is required to pay this penalty when payment is late, with no discretion to waive it.8Office of the Law Revision Counsel. 31 USC 3902 Interest Penalties
The Act also keeps agencies from sitting on invoices while looking for problems. If an agency determines a payment request is defective, it must notify the contractor within seven days, identify every deficiency, and explain what needs correcting. Missing that seven-day window shortens the payment period for the corrected invoice, so the agency effectively penalizes itself for being slow to respond.9eCFR. 5 CFR 1315.4 Prompt Payment Standards and Required Notices to Vendors
Most states have their own prompt payment statutes for private construction contracts, though timelines and penalties vary. Some require payment within 20 to 30 days of an approved application; others tie the deadline to the owner’s receipt of funds from a lender. The statutory defaults only apply when the contract is silent, so checking state law before signing is worth the effort.
Lien Waivers and the Signing Trap
Every interim payment in construction comes with a paperwork exchange that protects both sides: the lien waiver. When a contractor receives a progress payment, the owner wants assurance the contractor will not later file a mechanic’s lien for the same work. The contractor provides that assurance by signing a waiver. The type matters.
A conditional lien waiver only takes effect once payment actually clears. The contractor signs when submitting an invoice or accepting a check, but if the check bounces, the lien rights remain intact. Look for language like “upon receipt of payment” or “provided payment is received.”
An unconditional lien waiver takes effect immediately on signing, regardless of whether the money has landed. Sign one before payment clears and if the payment fails, the lien rights are gone. The practical rule: sign a conditional waiver when you submit the invoice, and only sign an unconditional waiver after the funds have cleared your bank account.
Most progress-payment lien waivers specifically exclude retention from the waived amount, and they typically carve out extras not yet paid and contract rights related to breach or abandonment. Read the exclusions. Signing a waiver that inadvertently covers retention or disputed extras can cost real money at closeout.
Pay-When-Paid vs. Pay-If-Paid
Subcontractors receiving interim payments through a general contractor need to understand a distinction that can determine whether they get paid at all. Many subcontracts condition the subcontractor’s payment on the general’s receipt of payment from the owner, and the two versions behave very differently.
A pay-when-paid clause is treated as a timing mechanism. The general will pay the sub when it receives payment from the owner, but the obligation to pay still exists. If the owner is slow, the sub waits. If the owner never pays, the general still owes the money eventually.
A pay-if-paid clause shifts the risk of owner nonpayment to the subcontractor. Payment from the owner is a condition precedent: no owner payment, no obligation to pay the sub. Many states void these clauses as against public policy; they remain enforceable in others. A sub signing a pay-if-paid clause is agreeing to absorb the owner’s credit risk, which is rarely a sound trade.
Tax Timing on Interim Payments
How an interim payment hits your tax return depends on your accounting method. The IRS recognizes two approaches, and they produce different timing results.
Cash-method taxpayers report income in the year they actually receive it. A payment deposited in December 2026 is 2026 income, even if the work was performed months earlier.10Internal Revenue Service. Publication 538, Accounting Periods and Methods Most large contractors cannot use the cash method, because the IRS requires businesses above certain revenue thresholds to use accrual accounting.
Accrual-method taxpayers report income when all events have occurred that fix the right to receive payment and the amount can be determined with reasonable accuracy. In practice, the contractor reports income as work is performed and billed, even if the check has not arrived.10Internal Revenue Service. Publication 538, Accounting Periods and Methods The timing of the deposit does not control the tax obligation.
Retention gets special treatment that helps accrual-method contractors. Because the contractor does not have a fixed right to the retained amount until the owner accepts the completed project, the IRS generally allows accrual-method taxpayers to defer reporting retention as income until it becomes billable under the contract. Revenue Ruling 69-314 permits this election, but the contractor must be consistent: deferring retainage receivable requires also deferring retainage payable to subcontractors.11Internal Revenue Service. Construction Industry Audit Technique Guide On a large project with 10 percent retention, the deferral can meaningfully reduce tax liability during construction.
Final Payment and Reconciliation
The last payment on a contract is never just the remaining balance. It is a full reconciliation of everything that happened during the project: the original contract price, every approved change order, every interim payment made, and the accumulated retention.
It starts with a final inspection. The owner or architect walks the project, generates a punch list of incomplete or defective items, and the contractor works through it. Outstanding claims or disputes over change order pricing need resolution before the final number can be locked down. This is where lingering disagreements over scope or quality tend to surface, and it is where many projects stall for weeks or months.
Once the owner issues a certificate of substantial completion or final acceptance, the retained funds are released. The final payment equals the total adjusted contract price minus every interim payment already made, plus the full accumulated retention. On a $10 million contract with $500,000 in approved change orders and $1.05 million in accumulated retention, and where $9.0 million in interim payments have been made (net of retention), the final payment would be $1.55 million: the remaining contract balance plus the released retention.
Disputes that cannot be resolved by negotiation go to whatever process the contract specifies. Most construction contracts call for mediation first, followed by binding arbitration or litigation. Some include provisions for expedited arbitration on payment disputes, with proceedings designed to conclude within 90 to 180 days rather than running for years. Read the dispute resolution clause before signing, because by the time you need it, you are stuck with it.