What is a contractor cost-plus contract?
A contractor cost-plus contract is a pricing agreement that pays actual job costs plus a fee for overhead and profit, for jobs with unclear scope. Picture a remodeler opening the wall of a 1960s bathroom and finding a rotted subfloor underneath the tile.
On a fixed bid, the cost of that surprise comes straight out of the remodeler’s profit. With a contractor cost-plus agreement, the homeowner pays for the repair as a documented job cost, and the remodeler still earns the agreed fee. The difference decides who loses sleep when a job goes sideways.
Below, you’ll learn how cost-plus pricing works, the main contract types, how to do the markup math, and which pitfalls to avoid.
Key takeaways
- On cost-plus jobs, the owner carries the risk of rising costs, while the contractor carries the burden of documenting every expense.
- Build your cost-plus fee from your overhead rate plus your target profit, then check the margin it produces.
- A guaranteed maximum price caps the owner’s total bill, with changes allowed only through approved change orders.
- Define reimbursable costs in writing before any work starts.
What is a cost-plus contract in construction?
A cost-plus construction contract reimburses the builder for every documented cost of the work, then adds an agreed fee on top.
Most contractor cost-plus agreements count these items as reimbursable costs, meaning costs the owner agrees to pay back:
- Labor: Wages and payroll costs for crew hours spent on the job.
- Materials: Lumber, drywall, fixtures, fasteners, and other supplies installed on site.
- Subcontractors: Invoices from electricians, plumbers, and other trade partners.
- Equipment: Rental fees and use charges for lifts, saws, and other tools.
- Permits: Building permits, inspection fees, and similar job-specific charges.
The “plus” side is the fee. It covers your overhead (costs of running the business that don’t belong to one job, such as office rent and insurance) and your profit. The fee can be a flat dollar amount or a percentage of costs.
Cost-plus jobs run on open-book billing, which means the owner can review the invoices, receipts, and time records behind every charge. Here’s a simple dollar example. A job with $60,000 in documented costs and a 20% fee adds $12,000, for a total bill of $72,000.
Cost-plus pricing fits jobs that nobody can fully price on day one. Common examples include:
- Custom homes: Owners pick finishes as construction moves along, so final costs stay open.
- Old-house remodels: Hidden wiring, plumbing, or rot may show up only after demolition.
- Insurance restoration: Fire and water damage repairs may need to start before the full damage is known.
- Design-build additions: One firm designs and builds the addition, so work may begin while drawings are still evolving.
Open books only hold up if your records do. Tie every box of tile and length of pipe to its job, with a purchase record attached.
To learn how to assign labor, material, and overhead costs to each project, take a look at our guide to job costing.
How is a cost-plus contract different from a fixed-price contract?
The biggest difference is who carries the risk, because a fixed-price contractor commits to one total before work begins. A fixed-price deal is also called a lump-sum contract.
| Factor | Cost-plus contract | Fixed-price contract |
|---|---|---|
| Pricing basis | Actual costs plus an agreed fee | One price set at signing |
| Who bears overrun risk | Owner | Contractor |
| Who keeps savings | Owner | Contractor |
| Scope needed at signing | Rough scope is enough | Complete plans and specs |
| Paperwork | Heavy, with receipts and time records | Lighter, with progress billing |
The American Institute of Architects (AIA) publishes standard construction contract forms, including guaranteed maximum price (GMP) agreements. Its 2026 AIA guide to GMP contracts explains that a fixed-price contractor keeps any savings and absorbs any overruns. A traditional cost-plus deal, by contrast, has no maximum project cost.
Why do contractors use cost-plus contracts?
Contractors use cost-plus contracts to shift the risk of unknown costs to the owner while still earning a predictable fee. The approach fits jobs where pricing everything upfront would mean guessing.
1. Protection from material price swings
Material prices can move a lot between bid day and buying day. The National Association of Home Builders (NAHB) tracks those swings.
Its 2026 NAHB building material price analysis found residential material prices excluding energy rose 5% year over year in July 2026. Based on Bureau of Labor Statistics data, NAHB called it the largest yearly jump since December 2022.
In the July 2026 NAHB builder material cost survey, run with Wells Fargo, builders reported a median 6.7% annual rise in material costs. Builders with five or fewer 2025 home starts reported 9.1%, compared with 1.8% for builders with 100 or more starts.
On a fixed bid, increases like these eat into your margin. A contractor cost-plus contract passes them through as documented costs. Accurate material records become the part of the job you can least afford to get wrong.
2. Room to handle unknown scope
Hidden conditions, evolving designs, and client selections all change what a job costs, and cost-plus pricing absorbs them without reopening the contract.
You’ll still use change orders, which are signed agreements that add, remove, or alter work. The arguments over them may shrink, though, because nobody has to defend a lump-sum price that no longer matches the job.
3. A faster project start
Work can sometimes start before plans are complete, depending on the contract and local rules. For emergency repairs and insurance restoration, waiting on a finished bid set may delay urgent work.
On design-build projects, your crew may be able to pour footings while the architect finalizes interior details.
4. More trust through open books
Clients see the same invoices and receipts you do, and an actual supplier bill can build more confidence than a bid alone.
Clean records turn transparency into a selling point. Tool and equipment use can count as a reimbursable cost too, if the contract allows it. You can see how to log each tool against the job using it with tool tracking software.
How do you calculate a cost-plus fee?
You calculate a cost-plus fee by finding your overhead rate, adding your target profit, and applying that markup to job costs. Markup means the percentage you add on top of cost.
Follow these five steps, using a midsize remodeling company as the example:
- Total annual overhead: Add up yearly costs that don’t belong to one job, such as rent, insurance, trucks, and office salaries. Example: $180,000.
- Overhead rate: Divide annual overhead by annual direct job costs. Example: $180,000 ÷ $1,000,000 = 18%.
- Add target profit: Add the profit percentage you want to earn. Example: 18% + 8% = 26% markup.
- Apply to job costs: Multiply the job’s costs by 1 plus your markup. Example: $200,000 × 1.26 = $252,000.
- Check margin: Divide the fee by the total bill to see your margin, meaning profit as a share of price. Example: $52,000 ÷ $252,000 = 20.6% margin, not 26%.
Before you set a rate, find every indirect cost with our guide to calculating overhead costs. You can double-check your numbers against our markup percentage formula.
Some contractors charge a flat fee instead. A $45,000 flat fee on a $250,000 estimate stays $45,000 even if costs climb to $280,000.
As of 2026, the federal statute setting federal CPFF fee limits (41 U.S.C. 3905) generally caps cost-plus-fixed-fee (CPFF) fees at 10% of estimated cost. The statute sets different caps for research and development work (15%) and architect-engineer work (6%). Those caps cover US federal contracts only and set no limit on private jobs.
What are the types of cost-plus contracts?
Contractor cost-plus contracts come in five common types, each handling the fee and the owner’s budget differently. Some are defined mainly in federal contracting rules, while others appear in private contracts.
1. Cost-plus fixed fee (CPFF)
A CPFF contract sets the fee at signing. The Federal Acquisition Regulation (FAR) sets rules for US government buying. Per the 2026 FAR cost-plus-fixed-fee definition, the fee doesn’t vary with actual cost and gives only a minimum incentive to control costs.
2. Cost-plus percentage of cost (CPPC)
A CPPC contract ties the fee to costs, so the fee grows as spending grows. Some private contracts use a percentage fee because it’s easy to explain and bill.
In 2026, FAR 16.102 still lists a federal ban on CPPC contracting for US government work. Private jobs are a separate matter, governed by your contract and state law, so check with a lawyer before you sign.
3. Cost-plus incentive fee (CPIF)
A CPIF contract adjusts the fee by formula, comparing actual costs to an agreed target cost. Finish under target and you earn a larger fee, with the owner and contractor sharing the savings.
4. Cost-plus award fee (CPAF)
A CPAF contract pays a base fee plus an award amount judged on performance. The current FAR cost-plus-award-fee definition describes a base amount fixed at the start, which may be zero, plus an award from the government’s judgmental evaluation. The structure belongs to US federal contracting.
5. Cost-plus with a guaranteed maximum price (GMP)
A GMP contract adds a ceiling to cost-plus pricing, so the owner’s total bill can’t exceed an agreed amount. Contractors build the GMP from the cost estimate, the fee, and a contingency, which works as a reserve for unexpected costs. Size the contingency to the job’s risk.
Run the numbers on a sample job: a $300,000 estimate plus a 20% fee ($60,000) plus an 8% contingency ($24,000) equals a $384,000 GMP. The cap can move only through approved change orders.
If costs exceed the GMP without an approved change, the contractor generally pays the difference. When a job comes in under the cap, AIA notes some agreements return the savings to the owner, while others divide them by a negotiated provision.
What are the common pitfalls of cost-plus contracts?
Contractor cost-plus contracts can create disputes, cash-flow strain, and budget surprises when terms and records are loose. Watch for these six problems:
- Unclear reimbursable costs: AIA’s 2026 guidance notes that many GMP disputes start with vague cost definitions rather than the cap.
- No budget cap for the owner: Without a GMP, the final bill has no ceiling, which makes some owners nervous.
- Heavy documentation load: Every receipt, timesheet, and invoice needs to be saved, sorted, and matched to the right job.
- Cash-flow delays: Slow invoice reviews by owners can hold up your payments while supplier bills keep coming due.
- Weak cost-control incentive: Percentage fees reward higher spending, which can strain trust with owners.
- Scope creep without change orders: Small “while you’re at it” requests add up fast when nobody writes them down.
Lost receipts and untracked materials break open-book billing faster than any contract clause can. A pallet of shingles moved from one job to another without a record becomes a charge you can’t prove. For a closer look at tracking materials from purchase to installation, read our guide to material management in construction.
How Fishbowl helps you track costs on cost-plus jobs
Contractor cost-plus billing works when every cost has a record behind it, from the first purchase to the final walkthrough. Fishbowl’s construction inventory software tracks materials and purchase orders (POs) and syncs with QuickBooks, plus Xero through Fishbowl’s Xero integration. Take Stego Industries, a San Clemente, California maker of below-slab vapor barriers used in construction. By entering data once in Fishbowl, its fulfillment and logistics team works 20 fewer man-hours a week.
Frequently asked questions about contractor cost-plus contracts
Can a cost-plus contract be converted to a fixed price later?
Parties can agree in writing to change the pricing method, such as moving remaining work to a fixed price once drawings and selections are final. Have a lawyer review the amendment before anyone signs it. The amendment should also spell out how costs already incurred get settled, so any new price starts from real numbers.
Is it normal to pay a contractor a deposit upfront on cost-plus?
A deposit is a normal request, and it can cover early material orders, permits, and mobilization (getting crews and equipment to the site). Rules vary by state, so check your state’s contractor licensing rules and your contract’s payment terms. For example, California’s contractor down payment limit caps home improvement down payments at $1,000 or 10% of the contract price, whichever is less.
Do contractors mark up subcontractor invoices under cost-plus?
It depends on the contract, but when subcontractor invoices count as a cost of the work, the fee applies to them like any other cost. Some contracts set a lower fee on subcontractor work or exclude large specialty contracts from the fee entirely. Owners can ask to see each original subcontractor invoice next to the marked-up line on the bill.
What records should a homeowner ask for on a cost-plus job?
Ask for itemized invoices with receipts, subcontractor bills, time records, a change order log, and lien waivers (signed forms confirming suppliers and subcontractors were paid). Unpaid trade partners may have lien rights, meaning a legal claim against your property, depending on your state. For a California example, the Contractors State License Board (CSLB) explains notices and waivers in its CSLB guide to preventing mechanics liens.
Is a cost-plus contract more expensive than a fixed bid?
Not always, because a fixed bid may include a cushion for risks the contractor can’t see, and the owner pays it either way. On a cost-plus job, the owner pays only what the work actually costs, plus the fee. Totals still climb when owners keep adding upgrades, so review spending at every billing cycle.