Arizona doesn’t use a traditional sales tax on construction work. Instead, contractors pay Transaction Privilege Tax (TPT) under specific classifications that work very differently from what you’d find in most other states. The rules change depending on whether you’re a prime contractor, subcontractor, owner-builder, or spec builder. Getting the classification wrong is one of the most common TPT filing mistakes in Arizona, and it’s one of the most complex areas of TPT overall.

Prime contractors are taxed under the prime contracting classification. The taxable amount is 65% of the total contract price, which represents the presumed materials portion of the job. The other 35% is considered labor and is not taxed. So if you have a $100,000 contract, you owe TPT on $65,000. The rate depends on the job site location since Arizona TPT rates vary by city and county across the Valley. Prime contractors also get to deduct payments made to licensed subcontractors from their gross income before applying the 65% calculation. This deduction is critical because without it, both the prime and the sub would be paying tax on the same work.

Subcontractors are also taxed on 65% of their subcontract price under the same prime contracting classification. If you’re a sub doing $50,000 worth of work, your taxable base is $32,500. The same location-based rates apply. The exception is if the subcontractor is performing work that qualifies as exempt, such as certain government projects or work that meets specific exemption criteria.

Spec builders fall under a completely different classification. If you’re building a home or commercial property to sell rather than under contract with a buyer, you’re classified under the speculative builder category. Instead of being taxed on a contract price (there is no contract), spec builders are taxed on 65% of the sale price or the fair market value when the property is first offered for sale. The timing and calculation here catch a lot of builders off guard, especially those who transition between contract work and spec builds.

Owner-builders constructing a property for their own use don’t pay TPT the same way. Instead, they owe use tax on the materials they purchase directly. Since there’s no contract price, the 65% formula doesn’t apply. The tax is calculated on the actual cost of materials.

Where contractors get into trouble is filing under the wrong classification, forgetting to deduct subcontractor payments, or not accounting for the varying tax rates across different Phoenix metro cities. A job in Scottsdale has a different combined TPT rate than one in Mesa or Tempe. Filing at the wrong location rate creates underpayment or overpayment issues that compound over multiple returns.

Keeping your books organized by job and tracking subcontractor payments with proper documentation is essential for filing correctly. If your construction bookkeeping doesn’t clearly separate prime contract revenue from subcontractor payments, you’ll either overpay TPT or file inaccurately and deal with corrections later. Every subcontractor payment you fail to deduct means you’re paying tax on money that was already taxed at the sub level.

This is one area where getting professional help pays for itself quickly. Arizona’s TPT system for contractors is genuinely complex, and the penalties for incorrect filing add up fast. If you’re a contractor in the Phoenix area and aren’t confident your TPT filings are accurate, working with small business bookkeeping services that understand construction accounting can save you real money and a lot of frustration at filing time.