Works contract tax is the combined set of state sales and use tax rules and federal income tax rules that apply when a construction contract bundles physical materials with labor. Because ownership of the materials passes to the property owner only as the contractor installs them, neither a straight sales tax nor a straight income tax framework fits on its own. How you write the contract, how you report the income over time, and how you classify the people doing the work all change what you owe and to whom.
Lump-Sum vs. Separated Contracts
The biggest sales tax question on a construction job is whether the contract is written as a lump sum or as an itemized (separated) agreement. That single choice usually decides whether the contractor or the property owner ends up carrying the sales tax on materials.
With a lump-sum contract, the contractor quotes one price covering labor, materials, overhead, and profit. In most states the contractor is then treated as the final consumer of the materials, pays sales tax at the supplier counter, and does not charge the owner sales tax separately. Any markup on materials is folded into the bid price.
With a separated or time-and-materials contract, the contractor lists materials and labor as distinct line items. In many states this recasts the contractor as a retailer of the materials to the owner. The contractor buys the materials tax-free on a resale certificate and then collects sales tax from the owner on the marked-up selling price of those materials.
States do not follow this pattern uniformly, so contractors working across state lines need to confirm each state’s rules before locking in a contract format. On a $500,000 project, picking the wrong structure can push thousands of dollars of tax onto the wrong party or open up audit exposure that could have been avoided.
Use Tax on Out-of-State Materials
When materials come from a vendor that did not collect the destination state’s sales tax, use tax fills the gap. Use tax applies to goods stored, used, or consumed in the state when sales tax was never collected at purchase. Most states give a credit for sales tax already paid to another state, so the same materials are not taxed twice. On projects that pull steel, lumber, or fixtures from suppliers in several states, tracking which purchases already carried sales tax and which owe use tax is one of the more tedious pieces of compliance.
Federal Income Tax on Long-Term Contracts
On the federal side, the IRS treats any contract for building, constructing, reconstructing, or improving real property that does not finish within the tax year it starts as a long-term contract. These fall under Section 460 of the Internal Revenue Code, which generally requires the percentage-of-completion method.
The Percentage-of-Completion Method
Instead of waiting until the project is done to recognize the profit, this method makes the contractor report income each year based on how much of the estimated total cost has been incurred so far. The formula compares costs allocated to the contract and incurred before the close of the tax year with total estimated contract costs. Spent 40 percent of projected costs by year-end? You report 40 percent of the expected profit that year.
Estimates matter. Underestimating total costs in Year 1 inflates the completion percentage and pulls income forward; overestimating pushes it back. Either way, the look-back method reconciles it later.
The Look-Back Method and Form 8697
Once a long-term contract wraps up, the contractor compares the income reported in each earlier year (based on estimates) with what the income would have been using the final actual price and costs. If the earlier estimates caused underpayment of tax, the contractor owes interest on the difference. If they caused overpayment, the contractor gets an interest refund. The calculation is reported on Form 8697.
Look-back interest can also come up in later years, such as after a change order or a dispute settlement adjusts the contract price or cost. For contracts entered into after July 4, 2025, look-back does not apply to any contract completed within three years of its start date, an expansion from the earlier two-year window.
A small-contract exception cuts off look-back entirely for contracts whose gross price at completion does not exceed the lesser of $1 million or 1 percent of the taxpayer’s average annual gross receipts for the three preceding tax years. A de minimis exception applies when the cumulative income actually reported stays within 10 percent of the look-back income in every prior contract year.
The Small Contractor Exemption
Not every builder is pushed onto percentage-of-completion. Section 460(e) exempts residential construction contracts and other construction contracts the contractor estimates will be finished within two years, provided the contractor meets the gross receipts test under Section 448(c). For contracts entered into in 2025, that threshold was $31 million in average annual gross receipts over the three preceding tax years, adjusted annually for inflation. Contractors who qualify can use the completed-contract method or another permissible method and defer income recognition until the project is done. For most small and mid-size builders, this exemption is what keeps the tax accounting workable.
Retainage and When It Becomes Taxable
Retainage is the slice of each payment the property owner holds back until the project or a milestone is finished. For contractors on the percentage-of-completion method, retainage counts in the total contract price when calculating completion percentage, which means the contractor recognizes income on withheld amounts before the cash arrives. On multi-year projects where 5 to 10 percent of every draw is held back, that creates a real cash-flow squeeze.
Outside Section 460, the rules are gentler. Under general accrual rules, retainage usually is not included in income until the condition triggering its release has been met, such as final acceptance. Cash-method taxpayers simply report retainage when they receive it. Which method applies decides whether you owe tax on money you have not yet collected.
Repairs vs. Capital Improvements
Whether money spent on a building is a deductible repair or a capital improvement that has to be depreciated is one of the more common fights between taxpayers and the IRS. The tangible property regulations under Section 263(a) set the framework. A cost must be capitalized if it produces a betterment, a restoration, or an adaptation of the property to a new or different use.
- Betterment covers fixing a pre-existing defect, making a material addition or physical enlargement, or materially increasing the property’s capacity, productivity, efficiency, or output.
- Restoration covers replacing a major component or substantial structural part, returning property that has deteriorated beyond functionality to working condition, or rebuilding property to like-new condition after its class life ends.
- Adaptation covers changing the property’s use to something inconsistent with its original purpose when it was placed in service.
Work that fails all three tests is generally deductible as a repair or maintenance expense in the year paid or incurred.
De Minimis Safe Harbor
For smaller items, the de minimis safe harbor lets a business expense purchases below a set dollar threshold instead of analyzing each one. Businesses with an applicable financial statement can deduct up to $5,000 per invoice or item. Those without one can deduct up to $2,500 per invoice or item. The election has to be made annually on the return, and the amounts must also be expensed on the taxpayer’s books and records.
Reporting Payments to Subcontractors
Any business that pays $600 or more to a subcontractor during the year has to file Form 1099-NEC reporting the total nonemployee compensation. The form is due to both the IRS and the subcontractor by January 31 of the following year, whether filed on paper or electronically. Businesses filing 10 or more information returns in a tax year must e-file.
Late filing penalties escalate. Within 30 days late costs $60 per form. After 30 days but before August 1, $130 per form. After August 1 or not at all, $340 per form. Intentional disregard jumps the penalty to $680 per form. On a project with dozens of subs, a missed deadline can rack up tens of thousands in penalties before any tax is assessed.
Worker Classification
Construction is one of the industries the IRS scrutinizes most heavily for worker misclassification. The line between employee and independent contractor depends on three sets of factors: behavioral control (whether you direct how the work is done), financial control (who supplies tools, whether expenses are reimbursed, how payment is structured), and the type of relationship (written contracts, benefits, permanence). No single factor decides it; the IRS looks at the full picture.
Getting it wrong is expensive. For unintentional misclassification, the employer owes 1.5 percent of the wages paid for income tax withholding, 40 percent of the worker’s share of FICA, 100 percent of the employer’s matching FICA share, and a $50 penalty for every unfiled W-2. Intentional misclassification jumps to 20 percent of all wages paid and full liability for both the employee and employer FICA shares, with potential criminal fines up to $1,000 per worker and up to a year of imprisonment.
Under Section 6672, the IRS can also go after individual officers, managers, or other responsible persons who willfully fail to collect and pay over employment taxes. That penalty equals the full unpaid tax and stacks on top of the penalties above.
Estimated Tax Payments
Self-employed contractors and businesses that expect to owe $1,000 or more in federal income tax when the return is filed ($500 for corporations) must make quarterly estimated payments. The IRS splits the year into four payment periods with fixed due dates. Miss one and you get an underpayment penalty even if the annual return shows a refund.
The safe harbor is simple: pay at least 90 percent of the current year’s tax liability or 100 percent of the prior year’s tax, whichever is smaller. For contractors whose income swings with the season, the annualized income installment method can line payments up more closely with when revenue actually comes in, though it takes more detailed quarterly math.
Recordkeeping
Construction projects produce enormous paper trails, and the IRS expects records that can survive an audit years after the job is done. Revenue Procedure 97-22 sets the federal standards for electronic recordkeeping. A digital system must ensure accurate and complete transfer of records and be able to index, store, preserve, retrieve, and reproduce them. Records must be cross-referenced between the general ledger and source documents so the audit trail is clear.
The system also has to include reasonable controls against unauthorized changes, and reproductions must be legible down to every letter and number. If a contractor stops maintaining the hardware or software needed to reach stored records, the IRS treats those records as destroyed. Records must be kept as long as their contents could be relevant to the administration of any internal revenue law, which for most construction contracts means at least three years after the return is filed and often longer for contracts spanning multiple tax years.
In practice: keep every material invoice, subcontractor agreement, payroll record, change order, and payment receipt organized by project. During an audit, the IRS can require access to the storage system along with the hardware, software, and personnel needed to locate files. Contractors relying on disorganized folders tend to lose deductions they were legitimately entitled to, because they cannot produce the documentation when it counts.