A time and materials contract pays the contractor for hours actually worked at pre-negotiated hourly rates, plus the cost of materials used, under a written ceiling price that caps what the buyer owes. It’s the structure people reach for when the full scope of a job can’t be nailed down at signing: emergency repairs, custom software builds, consulting engagements, maintenance on aging systems. Drafted carefully, it shares risk sensibly between the parties. Drafted loosely, it becomes the format most prone to billing fights.
What follows is a working guide to the terms that matter, the records you need, and the deadlines and penalties that can bite either side.
How the Pricing Works
Every T&M agreement rests on two pricing pillars: labor and materials. Ambiguity in either is where most disputes start.
Labor Rates
The labor side uses fixed hourly rates that hold for the life of the contract. Each rate bundles the worker’s wages, overhead (benefits, insurance), and the contractor’s profit into one billable figure. Most contracts set different rates for different skill levels, so a senior engineer bills higher than a junior technician and the invoice tracks the expertise actually applied.
In federal work, labor categories and their rates are written into the contract schedule and can’t be changed without a formal modification.1Acquisition.GOV. 16.601 Time-and-Materials Contracts Private agreements should follow the same discipline. Vague category descriptions invite contractors to bill senior rates for junior workers, so spell out minimum qualifications where the skill level affects the deliverable.
Material Costs and Markup
Materials cover raw supplies, parts, equipment rentals, and shipping. The contract should define exactly which expenses count as direct material costs so the contractor can’t quietly fold in general business overhead. Federal rules treat raw materials, parts, subassemblies, and manufacturing supplies as material costs, and require the contractor to credit back any trade discounts, refunds, or rebates received.2Acquisition.GOV. 31.205-26 Material Costs
Contractors typically add a percentage markup on material purchases to cover procurement, storage, and handling. The percentage is negotiated and should be supported by the contractor’s historical accounting data. In federal T&M contracts, any indirect costs charged on materials must follow the contractor’s established written accounting practices and can only cover costs clearly excluded from the hourly labor rates.3Acquisition.GOV. 52.232-7 Payments Under Time-and-Materials and Labor-Hour Contracts Travel, third-party shipping, and equipment rental each need explicit treatment, or someone will argue later about whether they belong in materials or overhead.
When This Contract Type Fits
Federal acquisition rules restrict T&M contracts to situations where the scope or duration genuinely can’t be estimated with reasonable confidence at signing. Before awarding one, the contracting officer has to sign a written determination that no other contract type would work. The rules also require ongoing surveillance of contractor performance, because T&M pricing gives the contractor no built-in incentive to control costs or work efficiently.1Acquisition.GOV. 16.601 Time-and-Materials Contracts
No statute forces that analysis in private deals, but the same logic applies. T&M fits emergency repairs where the damage isn’t visible until demolition starts, research work where the path to a solution can’t be mapped in advance, and maintenance on aging systems where hidden failures keep surfacing. If you can define the deliverables and estimate the effort with reasonable accuracy, a fixed-price contract usually protects the buyer better.
What the Contract Must Say
A Ceiling Price
Every T&M contract needs a ceiling price, sometimes called a not-to-exceed amount. That’s the maximum the buyer is obligated to pay. A contractor who goes past it without a written modification absorbs the excess.1Acquisition.GOV. 16.601 Time-and-Materials Contracts In practice the contractor also has a duty to warn the client as spending approaches the cap. If work stops because the ceiling was hit without warning, the contractor usually bears the fallout.
Setting the ceiling too low creates its own problem: a work stoppage mid-task that leaves the buyer with nothing usable. Experienced parties set the number with a reasonable contingency buffer and pair it with progress-reporting milestones so neither side gets blindsided.
Labor Categories and Rates
List every labor category that could touch the project, from project managers down to administrative support, with a stated hourly rate for each. Attach minimum qualification requirements where skill level drives the work product. For construction, industry templates from organizations like the American Institute of Architects give useful frameworks.
Material and Indirect Cost Terms
State the markup percentage on materials and identify which indirect costs are reimbursable. Require vendor receipts for all material purchases so the buyer can verify both the underlying cost and the applied markup.
A Change-Order Process
T&M is especially vulnerable to scope creep because the flexible pricing makes it easy to keep adding work without anyone formally recognizing the change. Require written change orders for any work outside the original scope. In federal procurement, the contracting officer must negotiate the resulting price adjustment as quickly as practicable.4Acquisition.GOV. Subpart 43.2 – Change Orders
The private-sector principle is the same: no extra work without a signed written authorization that identifies what’s being added and how it affects the ceiling. When a change hasn’t been priced in advance, require the contractor to segregate those costs in their accounting so the parties can negotiate a fair adjustment later. Once the adjustment is settled, get a release of further claims on that change to close the door on repeat disputes.4Acquisition.GOV. Subpart 43.2 – Change Orders
Audit Rights
Without a contractual right to inspect the records, a client who suspects overbilling has no recourse short of litigation. A well-drafted audit clause gives the buyer or an independent auditor access to timesheets, vendor receipts, and payroll records on reasonable notice, and spells out the consequences for non-cooperation.
Termination for Convenience
Either side may need to end the work early without anyone being at fault. In federal T&M contracts, the government can terminate for convenience and must pay the contractor for all hours worked at the scheduled rates through the termination date, all material costs incurred, reasonable wind-down expenses, and the costs of settling terminated subcontracts, along with reasonable settlement costs such as accounting and legal fees.5Acquisition.GOV. 52.249-6 Termination (Cost-Reimbursement)
Private contracts should address convenience termination explicitly. A buyer who walks away without a termination clause may face a breach claim for the contractor’s lost anticipated profit on the remaining work.
Termination for Default
When a contractor misses deadlines, supplies unqualified workers, or fails to meet quality standards, the buyer can terminate for default. Federal rules require a written cure notice giving the contractor at least 10 days to fix the problem before termination takes effect.6eCFR. 48 CFR 49.402-3 – Procedure for Default One exception: when the contractor simply fails to deliver on time, no cure notice is required, though the government may need to set a new deadline if its own conduct could be read as waiving the original one.
Private contracts should mirror this structure. Define default, state the cure period, and say what happens to payment for partially completed work. Immediate termination with no cure period holds up in some jurisdictions and not others, so a reasonable notice window protects both sides.
Invoicing and Record-Keeping
Good records are the backbone of T&M billing. The contractor should track every hour on signed timesheets that correspond to the labor categories in the contract, with task descriptions detailed enough that the client can verify productive use of time. Entries like “project work, 8 hours” invite rejected invoices. Tie descriptions to specific deliverables or work phases.
Material invoicing needs itemized third-party vendor receipts showing the actual purchase price, plus a clear calculation of the agreed markup. Project managers should track cumulative spending against the ceiling throughout the project, not just as it nears the cap. The sudden halt when the ceiling is reached mid-task creates waste, delay, and friction that a running tally would have prevented.
For federal contractors, record retention runs three years after final payment, covering timesheets, material receipts, subcontractor invoices, accounting procedures, and any other documentation supporting the amounts billed.7Acquisition.GOV. 4.703 Policy If the contractor voluntarily keeps records longer, the obligation extends to match. Late submission of final indirect cost rate proposals extends the clock by one day for every day of delay.8eCFR. 48 CFR 4.703 – Policy IRS rules impose a separate baseline: generally three years for records supporting income and deductions, and at least four years for employment tax records.9Internal Revenue Service. How Long Should I Keep Records
Payment Deadlines and Late-Payment Interest
Late payment on federal contracts triggers automatic interest under the Prompt Payment Act. The standard deadline is the later of 30 days after the billing office receives a proper invoice or 30 days after the government accepts the work.10Acquisition.GOV. Subpart 32.9 – Prompt Payment If the agency misses the deadline, it owes interest without the contractor having to ask. For the first half of 2026, the prompt payment interest rate is 4.125% per year.11Federal Register. Prompt Payment Interest Rate; Contract Disputes Act Interim payments on federal T&M contracts are made on the 30th day after the billing office receives a proper invoice, with the clock pausing if the government audits a specific request.3Acquisition.GOV. 52.232-7 Payments Under Time-and-Materials and Labor-Hour Contracts
If the agency fails to pay the interest penalty itself within 10 days of the late invoice payment, an additional penalty applies, but only if the contractor submits a written demand within 40 days of the invoice being paid.10Acquisition.GOV. Subpart 32.9 – Prompt Payment Miss that 40-day window and the additional penalty is forfeited. Contractors overlook it constantly.
Private-sector T&M contracts get no benefit from the Prompt Payment Act. Payment terms and late-payment interest need to be written into the agreement itself. Most states permit contractual interest on overdue commercial payments, but enforceable rates and caps vary by jurisdiction. A contract silent on late payment makes collecting interest far harder.
Fraudulent Billing Exposure
Submitting inflated hours or fabricated receipts on a federal T&M contract is a federal crime. Under the False Claims Act, a person who files a fraudulent claim against the government faces up to five years in prison.12eCFR. 20 CFR 429.211 – Are There Any Penalties for Filing False Claims On the civil side, each false claim carries a penalty of $5,000 to $10,000 (adjusted upward for inflation each year, now substantially higher) plus three times the government’s damages.13Office of the Law Revision Counsel. 31 USC 3729 – False Claims A $100,000 overbilling can mean $300,000 in damages before per-claim penalties and the government’s litigation costs.
A narrow safe harbor exists. If the contractor discloses the false billing to investigators within 30 days of discovering it, cooperates fully, and no enforcement action has already begun, the court may reduce the damages multiplier from three times to two times.13Office of the Law Revision Counsel. 31 USC 3729 – False Claims Still a heavy penalty, but it rewards prompt self-reporting over cover-ups.
In private contracts, intentional overbilling typically gives rise to breach-of-contract and fraud claims under state law. The contract itself should state that intentional overbilling is grounds for immediate termination and forfeiture of disputed amounts, and that the contractor is liable for the buyer’s audit and legal costs incurred in investigating the fraud.