Ask a contractor what a kitchen remodel actually cost them and you'll usually hear the bid price repeated back with more confidence than it deserves. What it really cost — lumber that spiked mid-job, a rented lift kept two extra days, gas running between three job sites — rarely gets tallied until tax season, if it gets tallied at all.
Job costing means tracking what a specific job actually costs, in real time, against the bid — not reconstructing it from bank statements the following April. It's the same receipts you're already collecting, just tagged to the job instead of stuffed in the truck's glovebox.
What job costing actually means for a contractor
One habit, repeated every time money leaves your account or your wallet on a job: tag it to that job, not a general "materials" bucket. Do that consistently and you get a live, job-by-job picture of spend versus bid — instead of finding out a job barely broke even after the client's already paid and moved on.
The costs that quietly eat your margin
- Materials & supply runs — lumber, fixings, plumbing and electrical stock, paint. Easy to track on one big invoice, easy to lose across three small runs.
- Mileage & vehicle costs — truck running costs between job sites, tracked via the standard mileage rate or actual expenses.
- Subcontractor labor — anyone brought in to help on a job, especially those you'll need to issue a 1099-NEC to at year end.
- Equipment rental — lifts, compactors, generators — day-rate costs that belong to one job.
- Consumables & PPE — blades, screws, sealant, safety gear. Small, constant, and rarely tracked properly.
- Tool replacement — the drill that went missing off the truck, the blade that snapped mid-cut.
None of these look big alone. Together, on a mid-sized job, they're often the gap between a real margin and a job that just about paid for itself.
Spreadsheet vs app
| Method | Set-up effort | What actually happens |
|---|---|---|
| Glovebox / shoebox | None | Receipts fade or blow out the truck window, no job-level view ever. |
| Spreadsheet | Medium | Works for a week, dies the first time you're too tired after a long shift to type it up. |
| Full bookkeeping software | High | Built for a desk, not a job site. Too many steps mid-job. |
| Purpose-built app (like Site Wallet) | Low | Snap the receipt, tag the job, done in under 10 seconds. |
A worked example: kitchen remodel
Say you bid a kitchen remodel at $18,000, budgeting $6,500 in materials and $2,200 for a subcontractor electrician. If every receipt gets tagged to "Kitchen — Ramirez" as it happens, by invoicing time you already know: materials ran to $7,300 after a supplier price bump, plus $250 in unplanned equipment rental. That's $18,000 bid against $9,750 in tracked job costs — a real margin figure, not a guess made after the fact.
What the IRS actually wants from you
- Schedule C — as a sole proprietor, business income and expenses are reported on Schedule C as part of your personal return, so accurate job-level records make that a rollup exercise, not a reconstruction.
- Self-employment tax — net earnings from self-employment are generally subject to self-employment tax in addition to income tax, which is exactly why accurately tracked deductions matter so much.
- Quarterly estimated taxes — most self-employed contractors need to pay estimated tax four times a year rather than waiting until filing season, based on expected income.
- Vehicle expenses — either the standard mileage rate (simpler, a fixed rate per business mile) or actual expenses (requires tracking real vehicle costs and the business-use percentage) — a mileage log is essential either way.
- 1099-NEC for subcontractors — generally required for any subcontractor you pay $600 or more in a year for services.
- Record-keeping period — the IRS generally recommends keeping records for at least three years, though longer periods apply in specific situations (the IRS itself suggests up to seven years for some claims).
This isn't tax advice — rules and thresholds change, so check irs.gov or your accountant for your situation. But whatever the current numbers, the habit stays the same: capture the receipt when it happens, tag it to the job, and let tax season be a formality instead of a scramble.
Mistakes that wreck job costing
- Mixing personal and business spending on one card, meaning every receipt needs manual sorting later.
- No per-job tagging — a single "materials" total tells you nothing about which job actually made money.
- Reconstructing the mileage log after the fact — the IRS expects contemporaneous records, and memory rarely does you favours anyway.
- Losing receipts before filing — thermal receipts fade fast, especially left in a hot truck cab.
- Never checking actual cost against the bid — the value of tracking is catching an overrun while there's still time to act.
How Site Wallet does this without extra admin
Snap a receipt and Site Wallet's AI reads the vendor, total, date and tax off it in about two seconds — faded thermal receipts included. Tag it to a job in one tap and watch a live, running per-job total build itself, so you can see a job's cost against its bid without touching a spreadsheet. Come tax season, export a PDF summary, a CSV for your bookkeeper, or a ZIP of every receipt photo — years of records kept safe either way.
FAQ
Do I need job costing if I'm the only one on the job?
Yes, arguably more so — as a sole operator there's no one else catching a job running over budget. Job-level totals are how you know which jobs are worth bidding on again.
How long do I need to keep records?
Generally at least three years, though the IRS recommends longer for certain situations — check current guidance or your accountant for your specific circumstances.
Does cash spent on a job still need tracking?
Yes. Cash spent on materials or a sub is still a business cost, and cash received is still taxable income — both sides need recording.
Standard mileage rate or actual expenses — which is better for job costing?
The standard mileage rate is simpler and needs less record-keeping beyond a mileage log. Actual expenses can capture a bigger deduction if your real vehicle costs are high, but requires tracking every vehicle-related receipt and the business-use percentage.