Most contractors sign whatever contract the owner presents without fully understanding how the contract type affects their risk position, their cash flow, and their operational requirements. A contractor who takes a cost-plus contract without GPS-verified construction time tracking is inviting a labor cost audit they can't pass. A contractor who bids lump sum on a project with ambiguous documents is pricing a risk they can't quantify.
This guide covers every major construction contract type — how it works, who bears what risk, what each type requires operationally, and how to choose the right type when you have a choice.
For contractors who want better visibility across contracts, labor, documentation, and job costs, construction management tools and features can help connect field activity with office reporting.
Construction contract types sit on a spectrum from maximum contractor risk to maximum owner risk:
MAX CONTRACTOR RISK ←————————————————→ MAX OWNER RISK Lump Sum Unit Price GMP Cost-Plus Time & Materials At the left: the contractor commits to a fixed price. Cost overruns are the contractor's problem. At the right: the owner pays actual costs plus a fee. Cost overruns are the owner's problem. Every contract type is a variation on where that risk line is drawn.
Contractor commits to completing the defined scope for a fixed price. Change orders adjust the price for scope changes. Everything within the defined scope is the contractor's responsibility at the committed price — regardless of actual cost.
Payment: Monthly progress billings based on schedule of values, tied to percent complete. Owner pays to the SOV regardless of what the contractor actually spent that month.
Documentation required: Standard — monthly pay applications with percent complete certification, lien waivers, stored materials documentation if applicable.
Contractor bears:
Owner bears:
Not required for owner billing — the owner pays the SOV regardless of actual hours. But construction time tracking for workers is essential for:
Using GPS timesheets for contractors helps document who worked, when they worked, and which jobsite they were on.
You can also use construction time tracking resources to improve how your team captures labor hours across contract types.
Owner pays all direct project costs (labor, materials, subcontractors, equipment, general conditions) plus a fee that covers the GC's overhead and profit. The fee is either:
Payment: Monthly billing of actual costs incurred, with supporting documentation, plus fee (prorated or as earned).
Cost-plus contracts grant the owner the right to audit the contractor's project cost records — usually for 3 years after project completion. Auditable records include:
This is where time tracking becomes non-negotiable. An owner auditing labor costs wants to see:
A construction employee time tracking app with GPS verification provides exactly this record — timestamped clock-ins with location stamps confirming the worker was at the project site, not at another job. Manual timesheets fail this audit routinely because they can't demonstrate site presence.
For contractors managing open-book work, construction photo documentation software can also support field records, progress updates, and backup documentation.
The contractor's company overhead is typically NOT a reimbursable cost — it's recovered through the fee. The fee must cover overhead and profit. Contractors who miscalculate their overhead rate and underestimate the fee end up with a fee that covers overhead but leaves no profit.
Some cost-plus contracts define which overhead items are reimbursable. Negotiate this carefully:
See How to Negotiate a Construction Contract for cost reimbursability definitions and fee structure negotiation.
Contractor bears:
Owner bears:
A cost-plus contract with a ceiling. Owner pays actual costs plus fee, but the GC guarantees the total will not exceed the GMP. If actual costs exceed the GMP, the excess is the GC's responsibility. If actual costs come in below the GMP, the savings are typically shared between owner and GC per a pre-agreed split.
GMP structure:
Contingency management: Who controls the GMP contingency is a critical negotiation point. Owner-controlled contingency requires owner approval to use. Contractor-controlled contingency is the GC's to use at discretion for unforeseen cost increases. Mixed structures are common — GC controls a portion, owner controls the rest.
When a project completes under the GMP, the savings split (often 50/50, sometimes 75/25 owner/GC) incentivizes the GC to control costs while giving the owner the benefit of a well-managed project.
Example: GMP of $2,000,000. Actual costs + fee = $1,800,000. Savings = $200,000. 50/50 split = $100,000 to owner (reduced final payment), $100,000 to GC (bonus above fee).
GMP contracts typically require the same open-book documentation as cost-plus, because actual costs determine the savings calculation. The GC must prove actual costs to establish what the savings are.
GPS time tracking and cost-code hour recording are essential for the same reasons as cost-plus — labor is the largest cost category and the most auditable. A GC claiming $800,000 in labor costs on a GMP project needs to show who worked, when, at what rate, on which scope.
Contractor bears:
Owner bears:
Work is defined by measurable units — cubic yards of concrete, linear feet of pipe, square yards of paving, tons of aggregate. The contractor commits to a unit price for each item. The total contract value is determined by the actual quantities installed.
Payment: Measured quantities at the end of each period × unit price = payment for that period.
Quantity variation clauses: Most unit price contracts allow repricing if quantities vary significantly from the estimates used in bidding (commonly ±15–25%). Large quantity decreases reduce the contractor's ability to recover fixed overhead.
Unit price contracts pay based on installed quantities — not hours worked. But construction crew time tracking is still essential for:
Owner pays for actual labor (hours × agreed rates), materials (actual invoice cost + markup), and equipment (hours × agreed rates or rental cost + markup). No pre-agreed scope or price limit.
T&M is used for:
T&M requires the most rigorous real-time documentation of any contract type. Every hour worked on T&M scope must be recorded at the time of work — not reconstructed. Every material purchase must have a receipt. Equipment use must be logged by hour.
Construction time tracking apps for construction with GPS verification are the foundation of defensible T&M billing:
Daily T&M tickets — summarizing workers, hours, materials, and equipment for the day — should be signed by the owner's representative each day. An unsigned summary submitted weeks later is a billing dispute waiting to happen.
Design-build is a project delivery method, not a payment method — it can use any of the above payment structures. The distinguishing feature is that the contractor is responsible for both design and construction under a single contract.
Payment implications:
Time tracking in design-build: Pre-construction labor (estimating, design coordination, preliminary engineering) should be tracked to the project cost code from day one. These hours are either recovered in the pre-construction fee or built into the construction cost — they need to be measured to be managed.
When the contractor has the ability to propose or negotiate the contract type:
|
Condition |
Recommended Contract Type |
Reason |
|---|---|---|
|
Complete, clear contract documents |
Lump sum |
Estimate risk is manageable; price certainty wins negotiated work |
|
Incomplete documents, trusted owner |
GMP or cost-plus |
Document gaps create lump sum risk; open book builds trust |
|
Unknown scope (renovation, demo) |
Cost-plus or T&M |
Can't price unknown scope responsibly as lump sum |
|
Public bidding required |
Lump sum or unit price |
Required by procurement law |
|
Ongoing owner relationship |
Cost-plus or GMP |
Transparency builds long-term partnership |
|
First time with this owner |
Lump sum |
Controls risk exposure until trust is established |
The worst outcome: Lump sum on a project with ambiguous or incomplete documents. The contractor owns every interpretation of the design. Change orders require proving the scope was outside the contract documents — on documents that weren't clear to begin with.
|
Contract Type |
Time Tracking Requirement |
Why |
|---|---|---|
|
Lump sum |
Recommended — not required |
Change orders, job cost control, productivity database |
|
Cost-plus |
Required — audit risk |
Owner can audit every labor hour billed to the project |
|
GMP |
Required — savings calculation |
Actual labor cost determines savings position |
|
Unit price |
Recommended |
Production rate monitoring; unit repricing support |
|
T&M |
Required — daily |
Every hour is a billing item; GPS verification prevents disputes |
The construction time clock app that works for cost-plus audit compliance also works for lump sum job cost control. The investment is the same; the benefit scales with contract type.
The same time tracking system can support every contract type.
The difference is how much the contractor depends on the records for billing, audits, and claims.
For general contractors managing multiple contract types, project management software for general contractors can help organize labor, photos, documentation, and project updates in one place.
For roofing teams working across service, repair, and project-based work, roofing contractor project management software can help connect crew tracking, documentation, and field communication.
Lump sum:
Cost-plus:
GMP:
Unit price:
T&M:
Construction contracts may define the payment rules, but field documentation proves the work.
That is why time tracking, photos, cost codes, and daily updates should be part of the project workflow from day one.
Contractors who want to improve project documentation and job cost visibility can compare TaskTag pricing plans to find the right option for their team.
You can also book a TaskTag demo to see how TaskTag supports labor tracking, jobsite documentation, and contractor workflows.
If you are ready to get started, you can create a free contractor account and begin organizing project information in one place.
For more helpful guides, visit the construction management resources library.
To learn more about the company, read About TaskTag.
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