Ask a contractor what a deck build cost them and you'll usually get a number that's really just what they quoted, repeated back with more confidence than it deserves. What it actually cost — lumber that went up in price mid-job, a rented compactor for two extra days, gas running between three sites — rarely gets tallied up until tax season, if it gets tallied at all.
Job costing means tracking what a specific job actually costs, in real time, against the quote — not reconstructing it from bank statements the following spring. It's the same receipts you're already collecting, just tagged to the job instead of tossed in the truck's centre console.
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 quote — 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 & supplier runs — lumber, fixings, plumbing and electrical stock, paint. Easy to track on one big invoice, easy to lose across three small runs.
- Fuel & vehicle costs — truck running costs between sites, tracked via a mileage logbook.
- Subtrades — anyone brought in to help on a job, invoiced or paid directly.
- Equipment rental — compactors, scaffolding, 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: deck build
Say you quote a deck build at $9,000, budgeting $3,200 in lumber and hardware, plus $900 for a subtrade to handle footings. If every receipt gets tagged to "Deck — Tremblay" as it happens, by invoicing time you already know: lumber ran to $3,650 after a price bump, plus $150 in unplanned equipment rental for an extra day. That's $9,000 quoted against $4,700 in tracked job costs — a real margin figure, not a guess made after the fact.
What the CRA actually wants from you
- Business income and expense records — as a sole proprietor, you report business income and expenses on the T2125 form as part of your personal tax return, so accurate job-level records make that a rollup exercise, not a reconstruction.
- GST/HST registration — generally required once your revenue exceeds $30,000 over four consecutive calendar quarters (the small supplier threshold). Once registered, you charge and remit GST/HST, and can claim input tax credits on eligible business purchases.
- Provincial variation — some provinces use HST (a combined rate), others charge GST plus a separate PST — worth knowing which applies where you work.
- Vehicle expense records — the CRA expects a mileage logbook distinguishing business from personal use, to support any vehicle expense claim.
- Record-keeping period — generally six years from the end of the last tax year they relate to.
This isn't tax advice — thresholds and rules change, so check canada.ca 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 time 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 CRA expects contemporaneous records, and memory rarely does you favours anyway.
- Losing receipts before filing — thermal receipts fade fast, especially left in a hot cab.
- Never checking actual cost against the quote — 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 quote without touching a spreadsheet. Come tax time, export a PDF summary, a CSV for your bookkeeper, or a ZIP of every receipt photo — six 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 quoting for again.
How long do I need to keep records?
Generally six years from the end of the last tax year the records relate to, though the CRA can request specific records be kept longer in some situations.
Does cash spent on a job still need tracking?
Yes. Cash spent on materials or a subtrade is still a business cost, and cash received is still taxable income — both sides need recording.
Do I need to register for GST/HST if I'm under the threshold?
Not usually, though voluntary registration is possible and sometimes worthwhile if you want to claim input tax credits on business purchases. Check with your accountant based on your situation.