How the New Residential Construction Rules Change Job Cost Accounting for Contractors

A contractor who spent fifteen years doing single-family remodels just broke ground on six townhomes, and the tax code finally caught up with him. Under the old rules, a project that size would have forced him to report income as the work got done, whether or not he'd been paid for it yet. Now he can defer that income until the project is substantially finished. That shift comes from a change to Section 460, the part of the tax code governing long-term construction contracts, and it changes the math on job cost accounting for contractors who are scaling past the four-unit ceiling that used to define "residential."

What actually changed

For years, the tax code drew a hard line at four dwelling units. A contract to build a single-family home, a duplex, or a fourplex could qualify as a "home construction contract" and skip percentage-of-completion accounting, meaning you didn't owe tax on projected profit before the cash showed up. Add a fifth unit to the same project and you lost that treatment, stuck reporting 70% of income under percentage-of-completion and only 30% under the exempt method, a blended approach that still pulled tax forward on work you hadn't been paid for.

The One Big Beautiful Bill Act rewrote that line. The exemption now covers "residential construction contracts" with no cap on unit count, and it stretches the expected construction period that qualifies a contract for the exemption from two years to three. It applies to contracts entered into in tax years beginning on or after July 4, 2025.

Who this actually helps

If you're still doing one remodel or one custom home at a time, this probably doesn't move your numbers, you were likely already exempt. It matters the moment you scale into small multifamily, a project that used to trip the old four-unit wall. Those jobs can now use the same deferral treatment as a single-family build: income gets recognized when the project is substantially complete instead of ratably as costs get incurred.

The three-year window helps a second group too. A custom home builder whose projects used to run long, permitting delays, material lead times, a client who changes the plan halfway through framing, could blow past the old two-year test and lose the exemption on a single-family job. That's a harder trap to see coming than the unit count ever was, because nobody plans for a project to run long. The extra year of runway means more of those jobs stay classified as exempt even when the schedule slips.

Why job cost accounting for contractors has to catch up

This isn't a set-it-and-forget-it change. Contract classification under Section 460 depends on numbers you have to document: when the contract was entered into, the expected construction period, and the cost estimates that put a project inside or outside the exemption. That's the same information your job costing should already be tracking project by project, but now it also drives which tax method applies to a job. A contractor whose job costing lives in a spreadsheet reconciled at tax time will struggle to prove eligibility if a project's classification ever gets questioned. A contractor whose job costs are tracked in real time, tied to actual start dates and updated estimates, already has the documentation sitting there.

Think about what that documentation actually needs to show: the date the contract was signed, the date the crew broke ground, and a cost estimate that gets updated as the job moves, not one frozen at bid time. Most contractors have pieces of this in a project folder somewhere. Few have it organized in a way that maps cleanly to a tax filing.

What to do with this

Pull the list of everything you have in progress or planned at five units or larger, or anything you assumed was stuck on percentage-of-completion because of the old four-unit rule. Check the contract date against the July 4, 2025 cutoff. Then look at how your job costing ties back to your books. If start dates and cost estimates for each project aren't documented in a way you could hand to someone reviewing your return, that's the gap to close before it costs you the deferral. Clean job cost accounting for contractors was always good practice. Now it's also the thing standing between you and a real tax deferral.

This is exactly the kind of change a generalist CPA misses, because it lives in the construction-specific corner of the tax code that most firms never open.

Download the $10K Tax Leak Checklist. It covers the seven areas where contractors overpay most, and contract classification on bigger jobs is one most firms never check. Most people find at least two or three they've never addressed.