Sales Tax on Materials for Commercial General Contractors

States generally split construction contracts into lump-sum (you owe tax on materials at purchase, the contract price to the owner isn't separately taxed) and time-and-materials (materials may be separately taxable to the owner, similar to a retail sale). A single GC often runs both contract types depending on the client, and using the wrong classification on a job means either overpaying tax on materials you didn't need to, or undercollecting from an owner you should have billed.

Start by listing every active state and confirming which classification applies to your typical contract structure there. Don't assume the classification your home state uses carries over; a handful of states treat the same contract language differently depending on local statute.

Government jobs, nonprofit-owned buildings, and some manufacturing or agricultural projects can qualify for a sales tax exemption on materials, but only if you collect and keep the right certificate from the owner before or at the time of purchase. Missing paperwork on an exempt job is one of the most common findings in a construction sales tax audit, because the exemption existed but nobody could produce proof of it.

The safest habit is treating the certificate as part of the contract package itself, collected and filed before the first material order goes out, not chased down after the project wraps and the paper trail has scattered across subcontractors and vendors.

A GC based in one state that wins a project across state lines usually creates nexus in the project state the moment work starts there, regardless of revenue thresholds that apply to remote sellers. This is different from the economic nexus rules that govern e-commerce, and it's easy to miss if your compliance approach was built around dollar thresholds instead of physical presence.

A single out-of-state project, even a modest one, can obligate you to register, file, and potentially owe use tax on materials brought across the state line, well before your total revenue in that state would trip an economic nexus test.

Avalara has real depth on the construction and contractor use case, including materials taxability by jurisdiction and support for the lump-sum versus time-and-materials distinction that general contractors run into constantly. Anrok, by contrast, was built for SaaS companies tracking economic nexus on subscription revenue; it isn't the right tool for a contractor buying lumber, steel and concrete across a dozen job states.

If your compliance need is materials-purchase tax rather than digital-product tax, Avalara or a construction-specific tax service is the realistic shortlist, not Anrok. Evaluate either option against your actual purchasing volume and number of active job states, not against a generic feature list.

Keep purchase records, exemption certificates and the contract classification decision together by job, from the day the contract is signed. Reconstructing this after a state audit letter arrives, once subcontractors have scattered and receipts are buried in a shared drive, costs far more staff time than filing it correctly the first time.

A simple job folder standard, one place for the contract type, the exemption paperwork, and the material purchase log, does more to reduce audit exposure than any single software decision.

Keep these records together in one folder for each job:

• Purchase records for the materials bought for that job, kept from the day the contract is signed rather than reconstructed after an audit letter arrives.
• Exemption certificates collected from tax-exempt owners such as government or nonprofit clients, obtained before or at the time of purchase.
• The contract classification decision, recording whether the job was treated as lump-sum or time-and-materials in that state.
• Registration details for the state where the jobsite sits, since starting work there generally creates nexus.

General contractors that assume every subcontractor is handling its own materials tax correctly are trusting a claim they never verify. A sub that misclassifies its own purchases, or doesn't register in a state where it's doing physical work, can create exposure that traces back to the GC on a joint audit, particularly on public projects where the state scrutinizes the whole project chain.

Ask subcontractors for their registration status in the job state as part of onboarding, the same way you'd confirm insurance coverage, rather than assuming it's handled somewhere else.