Ask an Arizona contractor how their Transaction Privilege Tax works and you will usually hear, “It depends on the job.” That is exactly right, and it is why Arizona contractor sales tax is so hard to file from an invoice list. Two invoices to the same homeowner, for the same amount, can land on opposite sides of the return. One is deducted in full. The other is taxed at the job-site city’s contracting rate, and it can drag earlier months with it.

We built the contractor side of CactusComply with a Phoenix-area landscape design-build company as our pilot. Of the first eight jobs we classified for them, five were MRRA and three were Modification: one was over the line on the day it was signed, and two added new free-standing structures. One of the MRRA remodels sits about $2,000 under its line. We also put our hardest open questions to the Arizona Department of Revenue (AZDOR) in writing, and its Tax Policy team answered in October 2026. This guide is everything we learned, in plain English. Watch the 90-second explainer, then we’ll break down the numbers.

Watch: one change order can make the whole job taxable

90 seconds on the 25% line, the change-order cushion, and why your rate is the job site’s, not your shop’s.

The two buckets: MRRA and Modification

All of your prime contracting revenue goes on the return as business code 015 gross. What happens next depends on how each contract is classified. The statute is clear that each contract stands on its own, so the unit is the contract, not the address and not the customer.

• MRRA (maintenance, repair, replacement or alteration). The contract is deducted with deduction code 500. The materials are taxed once instead: either you paid tax at the counter, or you report their cost under business code 315.
• Modification. The contract is taxable. The 35% labor deduction (502) comes off, so you are effectively taxed on 65% of the price, at the contracting rate of the city where the job is, not where your shop is.
• Subcontracted work. When a sub holds your Form 5005, their portion comes off with deduction 550.

“Where the job is” matters more than most crews expect. Our pilot’s jobs are spread across five Maricopa County cities, and the 015 rate is different in every one:

The 25% line, and the cushion that sits above it

For residential property, an alteration stays MRRA while the contract is at or under 25% of the property’s full cash value (land plus improvements, from the county assessor). For other property, the line is $750,000. The value is pinned to the date of the bid or the contract, whichever is higher. AZDOR confirmed to us that it means the value posted on the assessor’s site or Notice of Value as of that date, so a later assessor refresh does not re-test the job.

Two more rules catch people. First, a job that is over the line at signing is Modification from day one; the cushion only covers growth after signing. One of our pilot’s Tempe remodels was signed at roughly four times its line, so it was never MRRA. Second, the 15% de minimis rule: if ground-up work, such as a new block wall, ramada or pool, is more than 15% of the contract, the whole contract is Modification. AZDOR’s own example is a backyard outdoor kitchen with a gazebo. The Phoenix remodel above includes about $8,600 of ground-up work, under its 15% limit of roughly $22,000, so it stays MRRA.

Want your own numbers instead of ours? Run the job through the free classifier and it draws this line for your property.

What a flip costs: the Phoenix job in dollars

Take that Phoenix remodel. Phoenix’s live prime contracting (015) rate is 9.1%: 6.3% state and Maricopa County plus 2.8% city, the highest of our pilot’s five cities. The contract was signed at $148,000, just under the $150,000 line. Now suppose the homeowner adds a fire pit, more pavers and lighting, and $42,000 of change orders bring the total to $190,000, past the $187,500 cushion limit.

The point is not to scare anyone off change orders. It is knowing before you sign them. If you know the job has $39,500 of cushion left, you can price the change order, write it as a separate contract when the scope really is new, or go in with eyes open. A change order outside the original scope is its own contract and is tested on its own.

When a change order flips a job: amend OR request the credit, never both

Picture that change order landing in November on a job that has been MRRA since summer. September’s and October’s invoices are now taxable too. This is the moment most contractors get wrong, so we asked AZDOR directly. The answer: pick one remedy.

Doing both double-counts the fix. CactusComply asks you to choose once per flipped job, then builds the matching to-do list: which months to amend, the Form 5000 and Form 5005 paperwork, and reminders before AZDOR’s recommended date if you chose the credit request.

Materials on deducted jobs: business code 315

If you buy materials tax-free (with a Form 5000) and install them on an MRRA job, you owe tax on their cost under business code 315, the MRRA amount. The rules most people miss:

• It is the retail rate, on both sides. 315 is reported on the state/county lines and the city lines, at the retail rate, not the contracting rate. No labor deduction and no accounting credit apply.
• Report in the month the materials were installed. AZDOR confirmed that “used” means incorporated or installed, not delivered or staged in the yard. The purchase date only helps you find them.
• Report at the job site. Each job-site city gets its own 315 line, at cost, with no markup or delivery.
• No tax-free materials that month? Leave 315 off. AZDOR does not want a $0 line.
• Lawn maintenance is different. Materials used on maintenance service work go under use tax, business code 029, at the state rate plus any city that charges use tax. They are not 315.

You do not need 315 on your license before you use it. Add the code within the return and AZDOR adds it to your account.

Design fees: deductible at the state, not at the city

Design-build firms often bill a design fee and credit it toward the build. AZDOR’s answers here are specific:

• Deduction 690 is state and county only. It needs a written design contract, signed before the work starts, for design-phase or professional services, priced separately.
• Cities allow no design deduction. The only city-side relief is deduction 557 for an architect’s or engineer’s actual direct costs, and your books must show them separately (AZDOR ruling TPR 06-2).
• A design fee credited toward the build likely does not count toward the 25% test, because design is not alteration work. It still sits in your 015 gross. CactusComply lets you enter that design portion per job so the line test measures the right number.

Contracts signed before a rate change

Arizona lets a contract signed before a rate increase keep the old rate. AZDOR told us these contracts are reported under temporary business codes. For a city rate change, you take the bid or contract and proof of its date to the city, and the city assigns the code. CactusComply flags these jobs so they do not quietly go out at the new rate.

How it works in your monthly filing

Instead of tracking every job in a spreadsheet, you answer a few questions once per job and CactusComply carries them forward every month.

1. Upload your invoices. Export from BuilderTrend or QuickBooks and upload the file. Each invoice is matched to its job.
2. Classify Jobs. For each new job, a short wizard asks the job-site address, contract price, work type and any design portion. We pull the assessor’s full cash value and tell you MRRA or Modification, with the cushion left.
3. Add materials on deducted jobs. Enter tax-free materials in the month they were installed. They become 315 lines at each job-site city, or 029 for maintenance work.
4. Review and file. Your TPT-2 shows one line per job-site city with every deduction applied. We file it with AZDOR; you pay in AZTaxes.

What CactusComply watches for you

Spreadsheets can hold the rules. They cannot watch every job every month. CactusComply does.

Frequently asked questions

Is a backyard remodel taxable in Arizona?

It depends on the contract. An alteration on a home stays MRRA, and is deducted, while the contract is at or under 25% of the property’s full cash value and any ground-up work is 15% of the contract or less. Over that, the whole contract is Modification and taxed on 65% at the job-site city’s contracting rate. You can check a specific job with the free contractor job classifier.

What is business code 315?

315 is the MRRA amount: the cost of materials you bought tax-free and installed on a deducted MRRA job. It is reported in the month of installation, at the job site, at the retail rate on both the state and city sides. If you installed no tax-free materials that month, leave it off.

Do I report a job under my shop’s city or the job site’s city?

The job site’s city. AZDOR told us contractors keep their one existing location code and add one line per job-site city, the same way mobile vendors do. In Maricopa County alone the 015 rate runs from 7.8% in Chandler to 9.1% in Phoenix, so the city matters.

A change order flipped my job. Do I amend and file the MRRA Credit Request?

No, choose one. AZDOR says to amend when there are few or no subcontractors, and to use the MRRA Credit Request when there are many subs or the flip came late. The six months often quoted for the credit request is AZDOR’s recommendation, not a statutory deadline.

Are lawn maintenance materials reported under 315?

No. Materials used on maintenance service work are reported as use tax under business code 029, not 315.