A GMP contract, short for Guaranteed Maximum Price contract, caps the total amount an owner will pay for a construction project while reimbursing the contractor for actual documented costs plus a fixed fee. If spending stays below the cap, many agreements split the leftover funds between the owner and contractor through a shared savings clause. If costs exceed the cap without an approved change to the scope, the contractor absorbs the difference. The structure gives owners budget certainty and gives contractors a financial reason to build efficiently.
How a GMP Differs From Lump Sum and Cost Plus
A lump-sum, or fixed-price, contract locks in a single number for the whole project. The contractor keeps whatever margin remains after paying costs and owes you no view into the books. That works when drawings are complete and scope is settled, but you get no visibility into where your money goes.
A pure cost-plus contract sits at the opposite extreme. The contractor bills you for every dollar spent, adds a fee, and you pay. You see every invoice. There is no ceiling. If material prices spike or the schedule slips, your total keeps climbing. Cost-plus is common when a project needs to start before design is far enough along to price accurately.
A GMP contract takes the open-book transparency of cost-plus and bolts on a price ceiling from the lump-sum world. You reimburse documented costs and pay a fixed fee, but total spending cannot exceed the agreed maximum. This hybrid depends on both sides sharing financial records honestly, which is why GMP arrangements tend to appear between owners and contractors who already know each other.
What Makes Up the Price Ceiling
The guaranteed maximum price is not a single guess. It is assembled from several financial layers, and most disputes trace back to how these categories are defined in the contract.
Cost of the Work
This is the largest component: direct expenses required to physically build the project. It covers labor wages for workers on site, raw materials, equipment rental, and subcontractor payments. These costs pass through at their actual price without markup. The contractor submits invoices, timesheets, and purchase orders, and you reimburse as the work progresses.
General Conditions
General conditions are the indirect costs of running the job site, separate from the contractor’s home-office overhead. Typical items include superintendent and project-manager salaries while assigned to your project, job trailers and portable restrooms, temporary utilities, site security, debris removal, and permit fees. They are real and necessary, but they do not become part of the finished building. Spelling out which expenses fall into general conditions, which belong in the cost of the work, and which sit inside the contractor’s fee prevents arguments later.
Contractor’s Fee
The fee compensates the contractor for home-office overhead and profit. It is usually expressed as a fixed dollar amount or a percentage of the cost of the work, and it does not move when actual project costs fluctuate. Under federal construction rules, the fee can be adjusted only when a formal scope change justifies it, not simply because costs came in higher or lower than expected.1Acquisition.GOV. 536.7105-2 Guaranteed Maximum Price Private contracts generally follow the same principle.
Contingency
Contingency is a reserve built into the GMP for risks the contractor can anticipate but cannot price exactly, such as minor coordination issues, estimating gaps, or small design omissions. A well-drafted contingency clause makes the fund available only for the contractor’s use, with a defined draw process that typically requires documentation and sometimes owner approval. What happens to unused contingency depends entirely on the contract. Some agreements fold it into shared savings; others return it to the owner outright. If the contract is silent, expect a disagreement.
Adding the cost of the work, general conditions, the contractor’s fee, and the contingency gives you the guaranteed maximum price. The schedule of values then breaks that total into line items for tracking, but individual line items can go over their budgets as long as the overall GMP is not breached.2AIA Contract Documents. Summary – A102-2017 Standard Form of Agreement Between Owner and Contractor
When the GMP Is Set and What the Proposal Must Say
Timing matters. A GMP set too early, when design documents are still rough, forces the contractor to pad contingency to cover unknowns. Set too late, it delays construction. Federal construction guidelines call for establishing the price generally no earlier than 75 percent completion of construction documents.3eCFR. 48 CFR 536.7105-2 – Guaranteed Maximum Price Private projects follow similar logic: enough design detail to price accurately without waiting for every finish selection.
The industry’s most widely used frameworks are AIA Document A102, designed for a traditional owner-contractor relationship, and AIA Document A133, built for projects where a construction manager serves as both adviser and builder. Both adopt AIA Document A201 as general conditions governing day-to-day rights and responsibilities.2AIA Contract Documents. Summary – A102-2017 Standard Form of Agreement Between Owner and Contractor Contract documents include drawings, specifications, supplementary conditions, and an insurance and bonds exhibit.
The proposal itself must identify the drawings and specifications it is based on, including their date. This “basis of the GMP” is the single most important section for avoiding future disputes. Any assumptions the contractor made while pricing, any items excluded from scope, and any allowance figures for selections not yet finalized all belong here. An allowance is a placeholder for work that cannot be priced exactly at signing, such as countertop material or light fixtures the owner has not chosen. If an allowance item ultimately costs more or less than the placeholder, the GMP adjusts.
Parties should agree on the assumptions underlying the price. When the owner accepts those assumptions, any that turn out to be wrong may require revisions to the contract documents and a corresponding adjustment to the GMP.2AIA Contract Documents. Summary – A102-2017 Standard Form of Agreement Between Owner and Contractor
How Change Orders Move the Ceiling
The guaranteed maximum price is not permanently locked when you sign. It can move up or down through formal change orders. The most common triggers are owner-requested scope changes, unforeseen site conditions such as buried utilities or contaminated soil, and design errors discovered during construction.
Every adjustment must be documented in a written modification to the contract. Federal rules require a separate analysis explaining the rationale for each upward or downward change and a determination that the adjusted price is fair and reasonable.3eCFR. 48 CFR 536.7105-2 – Guaranteed Maximum Price Private contracts are not bound by those specific requirements, but the principle holds everywhere: both parties must agree to the scope change in writing before the GMP increases. A verbal “go ahead and add that” from the owner’s representative is not a change order and will not reliably protect either side.
Change orders that inflate the ceiling after signing are the most common source of disputes on GMP projects. The contractor should have accounted for all reasonably foreseeable costs in the original GMP. If change orders keep arriving, the owner needs to ask whether the original scope was poorly defined or the contractor is trying to recover margin through add-ons. If the owner keeps requesting upgrades, the contractor needs clear written authorization before spending a dollar on them.
Open-Book Accounting and Audit Rights
Because you are reimbursing actual costs, you need the ability to verify that every invoice is real, properly categorized, and within scope. GMP contracts are open-book: the contractor must give you access to the financial records behind every payment application.
Documents you should expect to review include original timesheets for on-site labor, payroll records, subcontractor invoices and payment applications, equipment rental agreements, and material purchase orders. The most useful audit practice is requesting the lowest-level source document rather than a summary report the contractor prepared after the fact. An original timesheet tells you more than a payroll summary built specifically to answer audit questions.
Federal cost-reimbursement contracts give the government explicit authority to examine and audit all records sufficient to reflect the costs claimed, including the right to inspect the contractor’s facilities at reasonable times.4Acquisition.GOV. 52.215-2 Audit and Records – Negotiation Private GMP contracts should include a comparable clause. Federal rules generally require contractors to retain financial documentation for three years after final payment.5Acquisition.GOV. Subpart 4.7 – Contractor Records Retention Private contracts set their own retention period, but three years is a reasonable baseline to negotiate. If your contract does not specifically grant the right to inspect financial records, you have a significant gap in your protection.
Shared Savings and Buyout Savings
Shared savings clauses align the contractor’s financial interests with the owner’s. Without one, the contractor has no particular reason to hunt for savings, because every dollar under budget simply returns to the owner. With one, the contractor keeps a portion of the gap between final cost and the GMP, creating a real incentive to negotiate better subcontractor pricing, reduce waste, and find efficiencies on site.
The split is negotiated before signing and expressed as a ratio. Federal construction rules limit the contractor’s share to between 30 and 50 percent, with higher percentages reserved for projects where the contractor takes on greater risk or complexity.6eCFR. 48 CFR 536.7105-5 – Shared Savings Incentive Private contracts can agree on any ratio. A 50/50 split is common, and some contracts go as far as 70/30 in the owner’s favor. If a project finishes $200,000 under the GMP and the contract specifies a 60/40 split favoring the owner, the owner receives $120,000 and the contractor keeps $80,000.
If the contract has no shared savings clause, unspent funds revert entirely to the owner. The GMP is a ceiling on reimbursement, not a guaranteed payout. The contractor receives documented costs plus the fixed fee and nothing more.
One commonly overlooked source of savings is the buyout, the process of soliciting bids from subcontractors and suppliers after the GMP is set. If the GMP includes $500,000 for mechanical work and the contractor awards the subcontract for $460,000, the $40,000 difference is a buyout saving. Most contracts require these savings to first offset any subcontractor packages that came in over budget. Whatever remains is typically returned to the owner through a deductive change order that reduces the GMP. Some contracts treat buyout savings differently from end-of-project savings, so read the specific language carefully.
The final savings calculation happens after the last subcontractor is paid and all work is accepted. The contractor submits a final accounting that reconciles every dollar spent against the GMP components. The owner reviews the documentation, confirms costs were legitimate and properly categorized, and applies the shared savings formula to any remaining balance. Thorough record-keeping throughout the project makes close-out straightforward. Gaps in documentation are the fastest way to turn a cooperative final accounting into a dispute.
Retainage and Liquidated Damages
Throughout the project, the owner typically withholds a percentage of each progress payment as retainage. The standard range is 5 to 10 percent, though many jurisdictions cap public-project retainage at the lower end of that range. Some contracts allow the retainage percentage to drop once the project reaches 50 percent completion. The withheld amount serves as security that the contractor will finish the work, complete the punch list, and resolve any deficiencies. Release of retainage usually happens after final inspection, punch-list completion, and submission of close-out documents including warranties and as-built drawings.
Many GMP contracts also include a liquidated damages provision that charges the contractor a fixed daily dollar amount for each day the project runs past the agreed completion date. This is not a penalty. It is a pre-agreed estimate of the actual harm the owner suffers from delay, such as lost rental income, extended temporary housing costs, or additional inspection expenses. For the clause to hold up, the daily rate must be a reasonable forecast of the owner’s probable damages, not an arbitrary number designed to punish.7Acquisition.GOV. Subpart 11.5 – Liquidated Damages Some contracts cap total liquidated damages at a fixed figure or a percentage of the contractor’s fee. The liquidated damages rate and any cap deserve the same negotiating attention as the contingency and shared savings percentages.
Where GMP Contracts Go Wrong
GMP contracts shift overrun risk to the contractor, but they are not risk-free for owners. The most common pitfalls fall into a few categories:
- Inflated contingency. A contractor nervous about an incomplete design will pad contingency to protect margin. If the pad is large enough, the GMP becomes functionally identical to a lump-sum price, and the cost-saving benefit disappears. Push for a contingency that reflects specific identified risks rather than a flat percentage.
- Incomplete design at GMP time. Setting the price before documents are sufficiently developed produces broad assumptions and a long list of exclusions. As design progresses, those exclusions turn into change orders. The maximum price keeps rising.
- Scope boundary disputes. If the contract does not clearly define what the GMP includes, disagreements arise over whether an unpriced item was an oversight, an exclusion, or an unforeseen condition. Unforeseen site conditions are typically the owner’s financial responsibility, so the line between “should have been in the GMP” and “nobody could have known” gets contested.
- Reduced competitive pressure. Because the contractor is selected before subcontractor pricing is finalized, the owner relies on the contractor to run a competitive buyout. Without transparency into how subcontractor bids are solicited and evaluated, there is a risk of inflated subcontract values that consume the savings potential before the project even starts.
The best protection against all of these is a contract that clearly defines the cost categories, spells out the contingency draw process, requires competitive bidding for subcontractor packages, and grants the owner meaningful audit rights. A GMP contract works when both sides treat it as a partnership built on shared financial information. When the open-book principle breaks down, so does every advantage the structure is supposed to provide.