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Is there sales tax on a new construction home in Idaho? How the contractor tax really works
The question behind the invoice
Every custom-home budget conversation eventually reaches it: is there sales tax on a new house? The Idaho answer surprises people. The contract to build on your land carries no sales tax line — but tax is absolutely in the number, because your builder paid it upstream, on every stick and fixture, at cost. The Idaho State Tax Commission’s contractor guide (last updated May 26, 2026) is unusually plain about how this works, and this page walks its own examples.
Rule one: the contractor is the taxpayer
“Idaho sales tax law says contractors are the consumers (end users) of all the goods they use. As a result, they must pay sales tax on all purchases, including all the equipment, tools, and supplies they use to build, improve, repair, or alter real property.”
— Idaho State Tax Commission, Contractors Working in Idaho. Retrieved 5 October 2026
Because the builder is the consumer of the materials — not a reseller — the builder cannot pass a tax line through to you on contracted work. And if the builder buys untaxed (say, from out of state):
“If a contractor buys or receives equipment and materials on which no one paid sales or use tax, the contractor owes use tax on the purchase. (Use tax is calculated at the same rate as sales tax.)”
— Idaho State Tax Commission, Contractors Working in Idaho. Retrieved 5 October 2026
There is no untaxed path. The only question is which pocket it comes from, which is why what “custom” actually means includes honest material pricing.
The Tax Commission's own worked example
The guide builds the same cabinets two ways. Installed in your home, the cabinetmaker is a contractor: tax on the $1,000 of materials at the supplier ($60 at the guide’s example 6% rate), no tax on the bill. Delivered loose for someone else to install, the same shop is a retailer: tax on the full retail price, labor included.
| The bill might read | Contractor (installed) | Retailer (delivered, not installed) |
|---|---|---|
| Job materials | $1,060 (tax already paid on the $1,000 at cost) | Materials to build cabinets $1,000 |
| Labor | $3,000 | Labor to build cabinets $2,500 |
| Sales tax on the bill | none | on $3,500: $210 (if the tax rate is 6%) |
| Total | $4,060 | $3,710 |
As the guide puts the contractor side: “The customer’s bill should include a materials cost of $1,060.” The $60 of tax is real — it is simply inside the materials line, not added at the bottom.
The sentence every customer should know
Tucked into the same example is a right most buyers have never heard of:
“(If sales tax is charged on the bill, the customer can refuse to pay it. If it’s charged in error and paid, the contractor must report and pay the sales tax collected to the state and still must pay tax on the materials.)”
— Idaho State Tax Commission, Contractors Working in Idaho. Retrieved 5 October 2026
A sales-tax line on a real-property contract is a red flag twice over: you may refuse it, and if you paid it by mistake, the builder still owes tax on the materials regardless — the money was never the state’s to take from you twice. This is one of the quiet protections worth keeping beside the paperwork rules that protect a build.
When sales tax legitimately appears
Plenty of lines on a build do carry tax — anything sold without being installed into real property. Freestanding furniture-style pieces, appliances the builder does not build in, materials you take delivery of yourself: those are retail sales. The mixed bill has a rule:
“Contractors bidding on a job with mixed contract services and retail goods must separate these items on their invoice to the customer and charge tax on only the retail portion”.
— Idaho State Tax Commission, Contractors Working in Idaho. Retrieved 5 October 2026
The guide’s illustration: installed kitchen cabinets (contractor side, no tax line) plus a freestanding china hutch (retail side, taxed with its labor) on one invoice, cleanly split.
The owner-provided materials trap
Some owners try to beat the system by buying materials themselves, tax-free or across a border, and hiring labor only. The state’s rule, current as of its July 1, 2026 amendment date, closes that door:
“When a project owner who isn’t exempt from tax buys materials for a job and hires a contractor to install them, sales or use tax is due when the material is purchased. If the owner doesn’t pay tax on the materials, the contractor is liable for the tax.”
— IDAPA 35.01.02.012.06.a, sales tax rule — contractors improving real property (rule text dated 7-1-26). Retrieved 5 October 2026
Read that closely: your unpaid tax becomes your contractor’s liability — which is exactly why a builder will either refuse owner-sourced materials or price the risk in. Nobody actually escapes the tax; they only move it.
Gravel, rock, and the corridor lot
The rule reaches the ground itself. A contractor who applies crushed rock is improving real property, and if the rock came from the owner’s own pit or a government source with no tax paid, tax is owed on its value anyway:
“The value of the rock is the "crushed value" — what a buyer would pay to a gravel pit owner for this type of product.”
— Idaho State Tax Commission, Contractors Working in Idaho. Retrieved 5 October 2026
On corridor lots, where driveway and road-base gravel is a real budget line, that detail matters: free rock is never quite free.
Down the chain, and up for sale
Subcontractors. The guide keeps liability local: when a sub furnishes and installs materials, the subcontractor pays the tax on those materials; if the general buys and furnishes materials instead, the general pays. Either way it never lands on your invoice as a pass-through.
Speculative builders. A builder who builds on their own land to sell later is still a contractor under the guide — the tax was paid on materials during the build, and the sale price of the finished house does not add a sales tax line. Buying a spec and buying custom work the same way on this point.
Out-of-state jobs. Form ST-103C lets contractors buy materials tax-free only for real-property work in no-sales-tax states — Montana, Oregon, Alaska — and the guide notes plainly that it “doesn’t apply to homeowners working on their own property.” It has no use on an Idaho build.
Read your bids with this in mind
- Expect no sales-tax line on contracted real-property work — tax lives inside the materials cost, already paid.
- Ask that retail items (freestanding pieces, uninstalled appliances) be separated and taxed on the retail portion only, as the rule requires.
- Challenge any tax line on contracted work with the guide’s own sentence — you may refuse to pay it.
- Do not buy materials yourself to dodge tax; the unpaid amount becomes your contractor’s liability and your problem.
- Want bids priced this way from the start? (208) 656-1516.
Sales tax is only one of the money rules wrapped into a build — the payment side is governed by how a construction lien works and the registration side by the contractor registration rule, and you can check any Idaho builder in minutes through the free state search. For where materials pricing sits in the whole number, see what a custom home costs in Ashton.
Common questions
Do I pay sales tax when I buy a new construction home in Idaho?
Not as a tax line. Idaho sales tax law treats the builder as the consumer of all materials, so tax is paid at cost when materials are bought and embedded in the contract price. The Tax Commission's contractor guide - last updated May 26, 2026 - shows the customer's bill including a materials cost of $1,060 on $1,000 of materials, with no tax added at the bottom.
Why doesn't my builder charge sales tax on labor and materials?
Because installing materials into real property makes the builder a contractor, not a retailer. The builder pays sales tax on materials at purchase (or use tax at the same rate if bought untaxed) and cannot charge tax to you on contracted work. Tax on your invoice would be double collection.
What if the builder's invoice shows a sales tax line?
The Tax Commission's guide says if sales tax is charged on the bill, the customer can refuse to pay it - and if it was charged in error and paid, the contractor must report and pay the collected tax to the state and still must pay tax on the materials. You can raise the guide itself in that conversation.
Are appliances and freestanding items taxed?
Yes, when sold without installation they are retail sales. A cabinetmaker installing kitchen cabinets acts as a contractor (no tax line), but a freestanding china hutch on the same invoice is retail - taxed on the full price including labor. Mixed invoices must separate the items and charge tax on only the retail portion.
Can I buy the materials myself tax-free and just hire labor?
No. IDAPA 35.01.02.012.06.a (rule text dated 7-1-26) says when a project owner buys materials and hires a contractor to install them, sales or use tax is due when the material is purchased - and if the owner doesn't pay it, the contractor is liable for the tax. Builders know this and price or refuse accordingly.
Who pays tax when the builder uses subcontractors?
Whoever furnishes the materials. If a subcontractor furnishes and installs materials, the subcontractor pays tax on those purchases. If the general contractor buys the materials and furnishes them to the sub, the general pays the tax. In both cases it stays off your invoice as a pass-through line.
Is sales tax on the contract price or the material cost?
Cost. The contractor pays tax on what the materials cost, not on the contract price. In the Tax Commission's example, $1,000 of materials draws $60 of tax at the guide's example 6% rate, and the customer's bill carries the $1,060 inside the materials line while the $3,000 of labor is untaxed.
What about gravel or rock from my own property?
Tax still applies. A contractor applying crushed rock is improving real property, and when the owner or an agency supplies the material untaxed, the contractor owes tax on the 'crushed value' - what a buyer would pay to a gravel pit owner for that product. Owner-supplied rock does not skip the tax.
Does buying a spec house add sales tax?
No. Speculative builders - who build on property they own to sell later - are contractors under the Tax Commission's guide. They paid tax on materials during construction, and the finished house sells without a sales tax line, the same as custom contract work on this point.
What is Form ST-103C?
A Sales Tax Exemption Certificate for real property contractors. It lets contractors buy materials tax-free only for jobs in no-sales-tax states - the guide names Montana, Oregon, and Alaska - or for qualifying production and agricultural-irrigation equipment. It does not apply to homeowners working on their own property, so it has no role in an Idaho build.
Is Idaho's sales tax rate 6%?
6% is the example rate the Tax Commission uses in its worked bills - the guide writes 'if the tax rate is 6%' when showing the $60 and $210 figures. The mechanics explained here (who pays, on what base, and what may appear on your invoice) hold at whatever rate applies when you build.