A cost-plus fee contract reimburses the contractor for the actual costs of doing the work and pays a separate fee on top as profit. It’s the arrangement owners reach for when the scope isn’t nailed down enough to price a fixed bid, and it’s common in federal procurement and in large private construction jobs. The tradeoff is simple to state and harder to manage: the contractor’s financial risk drops, and the owner’s rises.
How the Reimbursement Works
The structure has two parts. The owner pays every legitimate project cost the contractor incurs, then pays an additional fee for the contractor’s profit and management. Costs break into direct costs tied to the project, indirect costs that support it, and the fee. The contractor submits detailed records of what was spent, the owner verifies them, and payment follows on an agreed cycle, usually monthly.
Federal cost-reimbursement contracts live under Subpart 16.3 of the Federal Acquisition Regulation. Before award, the contracting agency has to find that the contractor’s accounting system is adequate, that a written acquisition plan has been approved above the contracting officer level, and that enough government resources exist to manage the contract.1Acquisition.GOV. FAR 16.301-3 Limitations The contract also sets a ceiling the contractor cannot exceed without the contracting officer’s approval.2Acquisition.GOV. FAR Subpart 16.3 – Cost-Reimbursement Contracts On private jobs, the same ideas apply, but what gets reimbursed and how is whatever the parties negotiated into the contract.
What Costs Get Reimbursed
Direct costs are the ones tied to specific project tasks. Labor is billed at actual wages plus the employer’s share of payroll taxes, which comes to 7.65% of wages (6.2% Social Security, 1.45% Medicare).3Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates Workers’ compensation premiums and any fringe benefits the contract names are also direct labor costs. Materials come in at purchase price after discounts, and equipment rentals count when the machinery is dedicated to the project. Each expense should trace back to a specific work item so the owner can compare spending to physical progress.
Indirect costs support the project without being part of the final building. Site trailers, portable sanitation, security fencing, builder’s risk and liability insurance allocated to the project, and professional services like architectural consulting for this specific job all qualify. Project manager travel, lodging, and meals during site visits typically fall here too. The dividing line is whether the cost exists because of this project. The contractor’s home office, corporate marketing, and executive salaries belong to the contractor’s general overhead and are handled separately under whatever the contract says.
On federal contracts, every reimbursed cost has to pass three tests at once: it must be reasonable, allocable to the contract, and allowable under the contract and applicable regulations.4Acquisition.GOV. FAR 31.201-2 Determining Allowability A cost that fails one of those can be rejected even if the contractor actually spent the money.
What Doesn’t Get Reimbursed
Not every dollar a contractor spends is eligible, and this is where disputes start. On federal projects, FAR Part 31.205 lists categories that are flatly off-limits. Entertainment, social activities, event tickets, meals at clubs, and gratuities cannot be charged.5Acquisition.GOV. FAR 31.205-14 Entertainment Costs Lobbying, political activity, fines and penalties, bad debts, losses on other contracts, and executive compensation above statutory limits are also unallowable. Including unallowable costs in a cost proposal can trigger penalties that effectively double the disallowed amount when the inclusion was knowing.6Acquisition.GOV. FAR 42.709 Penalties for Unallowable Costs
Private contracts don’t inherit those lists. Exclusions come from the contract language, and silence tends to work against the owner. If you’re the owner, this is the single most important place to negotiate hard. A detailed list of excluded cost categories, written before signing, prevents an argument later over whether a particular invoice should have been paid.
The Four Fee Models
The “plus fee” portion is the contractor’s profit, and the model you pick drives the contractor’s behavior for the life of the project. Four structures are common.
Fixed Fee
The fee is a specific dollar amount that doesn’t change with actual costs. Overrun or underrun, the contractor earns the same. The federal version caps the fixed fee on construction contracts at a percentage of estimated cost so the fee stays proportionate to the work.2Acquisition.GOV. FAR Subpart 16.3 – Cost-Reimbursement Contracts The owner’s problem with this model is that the contractor has no direct financial reason to control spending.
Percentage-Based Fee
The fee is a negotiated percentage of total project costs. Every dollar spent increases the contractor’s profit, which is the structural flaw. In residential construction, markups commonly run between 15% and 25%. Commercial and federal work tends toward lower percentages because the overhead spreads over bigger projects. Because this model rewards higher spending, it needs the most owner oversight.
Incentive Fee
A cost-plus-incentive-fee contract adjusts the fee based on how actual costs compare to a target. The contract sets a target cost, a target fee, minimum and maximum fee limits, and a sharing ratio. Come in under target and the fee goes up; run over and it comes down. A common sharing ratio puts 85% of overruns on the owner and 15% on the contractor, and the ratio can differ for underruns versus overruns.7Acquisition.GOV. FAR Part 16 – Types of Contracts – Section 16.405-1 Outside the range where the formula operates, the contractor just gets the minimum fee. This model builds in a real cost-control incentive without making the contractor absorb unlimited risk.
Award Fee
An award fee contract starts with a base fee, sometimes as low as zero, and adds an award based on the owner’s subjective evaluation of performance against criteria like schedule, quality, safety, and cooperation.8Acquisition.GOV. FAR Part 16 – Types of Contracts – Section 16.305 It gives the owner more flexibility than the incentive fee’s formula but can produce disagreements about fairness.
Capping the Owner’s Exposure: Guaranteed Maximum Price
Many private cost-plus contracts include a guaranteed maximum price, or GMP, that puts a ceiling on the owner’s total exposure. The contractor still gets reimbursed for actual costs plus the fee, but if the total goes over the GMP, the contractor absorbs the overrun. The GMP can only move up through formal change orders when the owner adds scope, not because the contractor underestimated or made mistakes.
When the project finishes below the GMP, a shared savings clause typically splits the difference, often 50-50. That gives the contractor a reason to find efficiencies without cutting corners on quality. To make sure the savings are real and not the product of inflated initial estimates, the owner needs audit access to the contractor’s books.
A GMP changes the risk profile of the whole contract. Without it, the owner’s exposure is open-ended. With it, the owner has a ceiling and the contractor still has upside through the savings split. For owners who want cost-plus flexibility but can’t live with an unlimited budget, a GMP is close to non-negotiable.
Risks the Owner Carries
Cost-plus solves the problem of getting contractors to bid work that isn’t fully defined, but it creates problems of its own. The biggest is the loss of cost predictability. Unlike a fixed-price contract, where the owner knows the total before breaking ground, a cost-plus arrangement doesn’t produce a final number until the last invoice is paid.
Incentives can also run against the owner. Under a fixed-fee or percentage model, the contractor doesn’t lose anything by taking longer or buying more expensive materials. Every extra week on site is more reimbursable labor and overhead. Incentive fees, GMP caps, and strong audit provisions are the counterweights, and they only help if they’re in the contract from day one.
Administrative burden is the other cost people underestimate. Someone has to review every receipt, verify every labor charge, and look at the contractor’s books. On a two-year project, that’s thousands of documents. Owners without in-house staff often hire construction managers or independent auditors, which adds another layer of cost. The transparency of cost-plus billing only matters if someone is actually reading the numbers.
Documentation, Audit Rights, and Retainage
Getting paid under a cost-plus contract means proving every expense. Contractors compile itemized receipts showing vendor, date, quantities, and the project code the materials were charged to. Labor is backed by certified payroll records showing each worker’s classification, hourly rate, and hours worked.9Acquisition.GOV. FAR 52.222-8 Payrolls and Basic Records Equipment rental agreements show the duration of use and the rate. In construction, the AIA G702 payment application and companion G703 schedule of values are standard formats for presenting all of this.10AIA Contract Documents. G702 Pay Application Form A schedule of values gives the owner a baseline to measure spending against physical progress by work category.11Construction Specifications Institute. Progress Payments, Schedules of Values, Part 1 – Fundamentals
Falsifying cost documentation on a federal contract is False Claims Act territory, with per-violation penalties plus treble damages on what the government lost.12Office of the Law Revision Counsel. 31 USC 3729 – False Claims On a multi-million-dollar job, padding invoices can produce liability large enough to end the business.
For federal construction, progress payments are due 14 days after the billing office receives a proper payment request, and final payment is due within 30 days after acceptance of the completed work.13Acquisition.GOV. FAR 52.232-27 Prompt Payment for Construction Contracts Private contracts set their own cycles. Monthly billing is standard.
Audit rights are the owner’s most powerful protection. A well-drafted audit clause gives access to invoices, payroll records, subcontractor agreements, and any other financial records tied to project costs. Without it, the owner is relying on the contractor’s self-reported numbers with no way to verify them. On federal contracts, audit rights are built into the FAR and aren’t negotiable. On private projects, the owner has to insist on the language before signing; adding it after work starts hands the contractor leverage to resist.
Retainage is the other standard tool. Most cost-plus contracts hold back 5% to 10% of each progress payment until the project is complete and punch-list items are resolved. That gives the contractor a reason to finish and fix deficiencies, since a real piece of their earned compensation is sitting with the owner. Many states cap the retainage percentage by statute, so the allowable amount varies by where the project is.
When This Contract Type Makes Sense
A cost-plus fee contract fits projects where the scope genuinely can’t be defined well enough to support a fixed price: renovations where conditions behind walls are unknown, research-driven work, early-phase construction where design is still evolving. It doesn’t fit projects where a competent bidder could price the work on complete drawings, because the owner gives up cost certainty with nothing to show for it. If you’re going to use one, pick the fee model with care, insist on a GMP if you need a ceiling, write the exclusions and audit rights into the contract before signing, and plan for the staff time to actually review the invoices. The protections in this type of agreement all work the same way: they’re only worth what you’re willing to enforce.