Do You Need a Sales Tax Exemption for Products You Use on the Job? 2026 Rules

Here is the short version, because it is the opposite of what most contractors expect at the counter. In California, you generally do not get a sales tax exemption for the products you use on the job. A construction contractor is treated as the consumer of the materials they furnish and install, which means you owe the sales or use tax on those materials yourself and you should not hand the supplier a resale certificate for them. A resale certificate — a form a genuine reseller gives a supplier to buy goods tax-free because the end customer will pay the tax instead — is for people who resell what they buy. When you build lumber and pipe into a structure, you are not reselling it. You are consuming it. (CDTFA Publication 9)

I see this backwards move all the time: a contractor tries to hand the supply house a resale certificate on lumber and pipe, figuring they will "resell" it inside the job. That is the mistake, not the savings. Pay the tax on materials at purchase. Only use a resale certificate for the items you genuinely resell as fixtures — and only under a contract that transfers title and separately states the fixture price. Below is how the split works, where the traps sit for HVAC, plumbing, roofing, concrete, and landscaping crews, and why the cleaning products in the back of your truck are always taxable to you.

This is a California-first walkthrough using CDTFA rules. Other states handle contractor sales tax differently — some let you use a resale certificate on materials — so if you work outside California, treat this as the framework and check your own state. For the bigger picture on how sales tax fits your overall setup, start at our contractor tax planning hub.

Do I pay sales tax on the materials I install?

Yes. In California, you pay sales tax on materials at the supply house, and you do not need a sales tax exemption for them. If you install the product into the structure and it loses its identity, you are the consumer, and the consumer pays the tax.

Under California Regulation 1521, a construction contractor is the consumer of the materials they furnish and install. You pay sales tax on the purchase of those materials, and you do not separately collect sales tax from the customer on them. Your customer pays you for the materials as part of the total job price, and the tax you already paid at the counter is part of your cost — it goes into your bid, not onto a separate tax line on the invoice. (CDTFA Regulation 1521)

The CA base sales and use tax rate is 7.25%, and district taxes stacked on by city and county push the total higher depending on where you buy or where the job sits. So a $10,000 lumber-and-drywall purchase is not a $10,000 cost — it is $10,000 plus at least $725 in tax before any district add-on. That is real money, and it belongs in the bid from the start, not discovered at the register.

What counts as materials versus fixtures for sales tax?

Materials lose their identity when affixed to real property. Fixtures keep their identity. That one distinction decides whether you pay tax as the consumer or collect tax as the retailer — and it is the whole game.

Materials are things like lumber, drywall, copper pipe, electrical wire, concrete, roofing shingles, paint, and insulation. Once installed, you cannot pull them out and resell them as what they were. The two-by-four that is now a wall stud is part of the building. You consumed it, so you pay sales tax when you buy it.

Fixtures — items that keep their identity after installation, like an air conditioning unit or a water heater — are different. An A/C unit sits in the system but it stays an A/C unit; it has a model number, a serial number, and an identity separate from the building. You are selling that unit to the customer, so on fixtures you are the retailer. You can buy the fixture with a resale certificate, install it, and then collect sales tax from the customer on its selling price.

On materials and supplies, the sales tax you pay is a cost you factor into your bid. On fixtures, the tax flows through to the customer — you collect it and remit it to the state. If you install fixtures across more than one city or county, the rate you charge depends on where the installation happens, which is its own layer we cover in our guide to handling sales tax across multiple cities and counties.

Can I use a resale certificate on tools, gas, and cleaning supplies?

No. Supplies you use up on the job but do not build into the structure are always taxable to you as the consumer. There is no resale or exemption route for consumed supplies — not in California, not for a bottle of degreaser, not for a tank of welding gas.

This category covers hand tools, power tools, gasoline, welding and cutting gases, thread-cutting oil (the lubricant used when cutting threads into pipe), solvents, rags, and cleaning products. You use them to do the work, but they are not part of what you sell to the customer. The saw blade wears down, the welding gas is consumed, the cleaning solvent evaporates. You are the end user of all of it, and you pay sales tax on every purchase. (CDTFA Publication 9)

This is exactly where the job-cleaning question lands. If you buy cleaning products — degreasers, mops, shop vacs, surface cleaners — to clean up the site at the end of the day, those are consumed supplies. You pay sales tax on them. You cannot hand the supplier a resale certificate for a bottle of degreaser any more than you can for a box of drywall screws. There is simply no version of the rule where consumed supplies get an exemption, because you never resell them.

The income tax side is a separate question, and I do not want you to conflate the two. Consumed supplies and tools may be deductible business expenses on your federal return, depending on cost and useful life. A $20 tube of caulk is a supply expense. A $2,500 concrete mixer is equipment you depreciate — deducting a big purchase in slices over several years — or expense in full using Section 179, the election that lets a business write off qualifying equipment in the year it goes to work. But paying sales tax on a purchase never stops you from deducting that purchase; the sales tax you paid is simply folded into your deductible cost. For the full write-off list, see our contractor tax write-offs guide and our breakdown of contractor equipment depreciation.

When can a contractor legally use a resale certificate?

Two situations, and only two. You can use a resale certificate when you are selling a fixture to the customer, or when your contract explicitly transfers title to the materials before installation and separately states the materials price on the invoice.

The first is straightforward. An HVAC contractor buys a furnace with a resale certificate, installs it, and charges the customer sales tax on the furnace's selling price. The contractor is the retailer of that furnace, so the resale certificate is exactly right.

The second is a contract structure that overrides the default consumer rule. If your contract says title to the materials transfers to the customer before you install them, and the invoice separately states the materials price apart from the labor, then you can act as the retailer of those materials — even materials that would normally be consumed. This is a specific treatment under Regulation 1521, and it only works if the contract language and the invoicing actually support it. A vague time-and-materials invoice with no title-transfer clause will not get you there. (CDTFA Regulation 1521)

Outside those two situations, issuing a resale certificate for materials you install is improper. The state can assess the tax you skipped plus interest and penalties. From what I have seen in practice, this is usually a straightforward billing problem when the CDTFA's records show resale certificates used on items that do not qualify — not a catastrophe, but a real, avoidable cost that grows the longer it sits.

Do I owe use tax on materials I buy out of state?

Yes. If you buy materials tax-free from an out-of-state supplier and use them on a California job, you owe use tax — the mirror of sales tax, owed when you buy something tax-free out of state and use it where the tax would have applied.

This comes up when you find a better price on lumber, tile, or fixtures from a supplier in Oregon or Nevada, and that supplier does not charge California sales tax because they have no presence in the state. The purchase arrives tax-free, but the obligation did not vanish — it shifted to you as the buyer. You owe use tax to the CDTFA on the purchase price, at the rate that applies where the materials get used. Since the CA base rate is 7.25% plus district taxes, that out-of-state "deal" often is not the discount it looked like once you add the use tax you owe.

If you are registered for a seller's permit in California, you report use tax on your sales and use tax return. If you are not registered — which is itself a problem if you sell fixtures — you report it on your state income tax return.

How do sales tax exemption rules differ outside California?

California's consumer-versus-retailer framework is one model, not the only one. Other states handle contractor sales tax differently, and some let contractors use a resale certificate on materials that California treats as consumed. If you work across state lines, do not assume the California answer travels with you.

Some states treat the contractor as the retailer of all materials installed under a lump-sum contract, allowing a resale certificate at purchase and requiring you to collect tax from the customer. Others follow California's approach. A few have specific carve-outs — government contracts, new residential construction, agricultural improvements — that override the general rule. And even within California, remember the two exceptions to the default: for fixtures you are the retailer, and for a contract that transfers title to the materials and separately states the price, you can act as the retailer of those materials too.

If you have nexus — enough presence in a state that its tax rules apply to you, like an office, a crew, or enough sales there — in more than one state, check each state's treatment before you decide who pays. The materials-versus-fixtures split is California's answer. Texas, Florida, New York, and others run their own versions, and they do not always agree on what counts as a fixture.

What are the most common sales tax mistakes contractors make?

In our work with trade contractors, the mistakes cluster around the same four errors. The first is using a resale certificate on materials you install. It feels like a savings at the register, but it builds a liability that grows until the state catches it. The second is the reverse — paying sales tax on fixtures you are reselling, which means you paid tax on your cost instead of collecting it on your selling price. You lose the markup spread, and the customer never sees the tax line they were supposed to pay.

The third is ignoring use tax on out-of-state purchases. The supplier did not charge it, so the contractor assumes nothing is owed. The obligation exists either way — it just moves from the supplier to the buyer.

The fourth is not registering for a seller's permit at all. If you sell fixtures — and most HVAC, plumbing, and electrical contractors do — you need a seller's permit to legally collect and remit the tax. Operating without one does not erase the obligation. It just means you are absorbing the tax out of your own pocket when the state eventually finds out.

What should I do to get this right?

Sort every purchase into three buckets: materials you install and consume, fixtures you resell, and supplies you use up. Pay sales tax on the first and third. Use a resale certificate only on the second — unless your contract genuinely transfers title to the materials and separately states the price. Track use tax on out-of-state buys. Register for a seller's permit if you sell fixtures, even occasionally.

From what I have seen, the contractors who stay clean on this are the ones who build the tax into their pricing from the start. They know which purchases are consumer purchases and which are retail sales before they walk into the supply house. They do not try to skip tax at the register and sort it out later. The rules are mechanical once you know the split, and the split is not subtle: if the item keeps its identity, you are the retailer; if it loses its identity or gets consumed, you are the consumer and you pay the tax.

If you are unsure where a specific purchase falls, work through the decision tree above, or check the CDTFA resources linked throughout this post. And remember this is California treatment — if your jobs cross state lines, confirm each state's rule before you decide who pays.

Not sure whether a purchase is a consumer buy or a resale? We help California trade contractors sort materials, fixtures, and supplies correctly, register for the right permits, and price the sales and use tax into their bids so it stops eating the margin. Book a meeting with our team here.