Materials, labor, and who owes the sales tax

A homeowner comparing bids forwards you a competitor's estimate for the same kind of job. Materials, labor, total. No sales tax line anywhere. You put tax on the materials of every job you write.

One of you is wrong — or you are in different states, and you are both right.

Every state casts you as the buyer or the seller

Before anything else, a state sales tax code decides what a contractor is when they install materials into a building. You are either the buyer of those materials or the seller of them, and the paperwork runs opposite either way.

The split exists because sales tax was written to tax the retail sale of goods, and construction does not fit. A water heater on a pallet is plainly a good. Once it is strapped, piped and vented, it is part of the building, and what you sold the homeowner is an improvement to real estate. So the state picks where the tax lands: at the supply house counter, or on the customer's bill.

The consumer model. The tax attaches at the supply house — the last moment the material was clearly a good. You are the end user. You pay sales tax to your supplier when you buy, and the customer's contract is treated as an improvement to real property rather than a sale of goods, so in the typical case there is no sales tax line on their bill at all. The tax is inside your cost. Which rate applies is its own question: some states source a counter pickup to the supplier's location and a delivery to the delivery address, and some look to where the material is finally used. Your state's sourcing rules decide that, not the sticker on the invoice.

The retailer model. The tax attaches at the job. You are reselling the materials, so you buy them tax-free on a resale certificate, collect sales tax from the customer on the materials portion, and remit it on your own return. The tax is on their bill — and it sits on your marked-up price rather than your cost, which is generally more tax.

Neither is more correct. Your state picked one before you were in business.

This is not the same question as whether your labor is taxable, which turns on what your labor did and how the invoice reads — that has its own guide. Nor is it the certificate paperwork, covered in resale certificates and exemptions. Settle this one first. Whether you buy the materials or resell them decides how both of those play out.

In some states, how you write the contract decides it

A fair number of states do not answer this once. They answer it per contract.

The distinction is usually lump-sum versus separated. A lump-sum contract quotes one price for the finished work. A separated contract — sometimes called time-and-materials — shows the materials charge and the labor charge as separate amounts to the customer. In several states that formatting choice moves you between the two models: lump-sum makes you the consumer, separated makes you the retailer of the materials.

Texas is the clearest published example. The Comptroller's guidance for contractors (publication 94-116, which sits on top of Rule 3.291) walks through both. The choice changes what you hand your supplier: a resale certificate under one, your money under the other.

In other states, how you write the contract changes nothing.

• Consistently a consumer. Pennsylvania is the example usually reached for: its guidance has long treated a construction contractor as the ultimate consumer of materials installed into real property, paying tax at purchase and not collecting on the construction contract. Several other states are commonly described the same way. Verify yours rather than assuming you are in that group.
• Neither model. Arizona does not levy a conventional sales tax at all. It taxes the privilege of doing business, and construction has its own classification, assessed on project receipts with a statutory standard deduction standing in for labor — and separate treatment again for maintenance, repair, replacement and alteration work. Take the current percentages and definitions from the Arizona Department of Revenue. A rule of thumb carried in from another state is worse than useless here.

One job, priced under both rules

A $2,400 job: $900 of materials at your cost, $1,500 of labor, a 30% materials markup, and a 7% combined rate. Use your own numbers — the point is the shape.

Priced correctly, the customer total is identical to the penny. That is not a coincidence — marking up a tax-inclusive cost and taxing a marked-up price are the same arithmetic. What differs is who holds the money and who files.

Use tax is the piece people forget. If you buy materials out of state, or pull stock from an inventory you originally bought on a resale certificate, no supplier collected anything. You still owe the tax, and you work it out yourself on your cost. Most state returns have a line for it, and unreported use tax is a routine audit finding.

Getting it wrong is expensive in both directions

Bidding as a retailer while the state treats you as a consumer. You price materials from the $900 on the invoice instead of the $963 you actually paid, so you bid $2,670 on a job that should have been $2,751.90. Nobody complains and nobody tells you. You are simply about $82 light on every job. A shop buying $300,000 of materials a year at a 7% rate is eating about $21,000 of tax it never charged for.

Buying on a resale certificate and never collecting. The state's position is that you took the materials tax-free and owe the tax you should have collected, plus penalty and interest — assessed years later, against jobs you cannot re-invoice.

Collecting tax you did not owe. Not the safe error people assume. Most states hold that anything you label "sales tax" on a customer's bill has to be remitted whether it was due or not, and getting it back to the customers is a refund process, not an adjustment.

Where your state answers this

Most states with a sales tax publish a bulletin written specifically for construction contractors. That is the document you want, not the general sales tax guide, and you should take the current edition from the agency's own site. If your work straddles categories — you sell and install appliances as well as remodel, or you fabricate before you install — ask for a written determination on your own facts and keep it. Ask again before your first job across a state line — the answer you have is your own state's, and the next state may have picked the other model.

Price from the cost you actually paid

If your state makes you the consumer, the number that belongs in your catalog is the landed cost with the tax in it, not the pre-tax figure on the supplier quote. Keep material costs in DoneQuote as what you actually pay at the counter and let the markup work from there, so the price you built is the price that reaches the customer on the estimate, the change order and the final invoice. If your state instead makes you the retailer on separated contracts, materials and labor have to stay on their own lines the whole way through, because the tax attaches to only one of them.