How to Track Business Expenses as a Contractor

Most contractors overpay taxes not because they cheated, but because they never had a system. The IRS estimates self-employed taxpayers leave an average of $2,000–$5,000 in deductions on the table each year — missed receipts, blurred job costs, forgotten mileage. A 30-minute setup now fixes that for every year ahead.

Get your categories right before you track anything

The biggest mistake contractors make is dumping everything into one bucket labeled “business expenses.” Without categories, you can’t see which jobs are profitable, and your accountant spends billable hours sorting your chaos in April.

Six categories cover the overwhelming majority of what a contractor spends:

• Materials & supplies — lumber, pipe, paint, concrete mix; anything bought for a specific job
• Labor & subcontractors — payments to subs and day laborers (1099s are generated from this bucket)
• Vehicle & mileage — fuel, repairs, registration, tolls if using actual costs; or the IRS standard mileage rate if you prefer simplicity (67¢/mile for 2024 — verify the current-year rate at IRS.gov)
• Equipment & tools — drills, compressors, ladders; items costing over $2,500 and lasting more than a year typically require depreciation rather than a full expense in year one
• Insurance & licensing — general liability premiums, contractor’s license fees, bond costs
• Marketing & admin — software, advertising, business cards, your accountant’s invoice

Pick these six buckets and apply them consistently. Switching category names mid-year creates reconciliation headaches you do not want.

The receipt rule most contractors get wrong

The IRS requires a receipt — physical or digital — for any business purchase over $75. A credit card statement alone is not enough. If the line item says “Home Depot $312,” that does not satisfy the documentation requirement — you need the itemized receipt showing exactly what was purchased.

A valid receipt must include:

• Vendor name and address
• Date of purchase
• Amount paid
• A description of items purchased (not just a total)

For vehicle mileage, the IRS wants a log with date, destination, business purpose, and miles driven. “Drove to job site” is not enough — “Drove to Jones deck project, 14 Maple Ave” is.

The easiest fix: photograph receipts immediately at the point of purchase. A phone photo is legally sufficient — the IRS has accepted digital records since Rev. Proc. 98-25. The ones that go missing are the ones left on a truck seat for three weeks.

Separate job costs from overhead

Job costs are expenses tied to a specific project: the $600 in materials for the Miller bathroom, the $850 you paid a sub to install tile. Overhead is what you pay whether you’re working or sitting at home: insurance, your truck payment, software subscriptions.

Keeping them separate gives you two things you can’t get any other way:

• Accurate estimates. If the Miller bathroom cost $1,400 in materials and $1,700 in labor, you know what to bid on the next similar job — not a guess, a data point.
• Real profit visibility. A job that looks like $3,000 in profit at the invoice level can be a wash once you allocate the hours you drove, the tool rental, and the sub’s markup. You need to see that before you price the next one.

Even a notes app with the job address and a running spend tally beats mixing everything together. Dedicated accounting software makes it faster, but the discipline matters more than the tool.

A 15-minute Friday routine that actually sticks

Contractors who stay on top of their books don’t do a big catch-up at tax time — they spend 15 minutes every Friday before they close up. The whole system collapses when receipts pile up for three months. A small weekly habit is dramatically less painful than six hours in a panic.

The routine:

• Photograph any paper receipts from the week and file them by job or category
• Log mileage for every job-site visit (your phone’s calendar has the addresses)
• Categorize any charges that hit your business card or account this week
• Flag any cash purchases you haven’t noted yet

That is the entire routine. It works because the cost per week is low enough that skipping feels worse than doing it.

FAQ

Do I need a separate business bank account?

Yes — it is the single highest-leverage move for a self-employed contractor. Commingled personal and business expenses make every audit riskier and every year-end more expensive. Most business checking accounts are free or close to it, and the separation saves you hours at tax time every year.

Can I deduct tools I already owned before starting the business?

Yes, at their fair market value at the time you converted them to business use. The burden of proof is on you: photograph each item alongside a comparable listing price showing what it would sell for used, and note the date. A written depreciation schedule from that point forward is then applied normally.

How far back can I claim expenses I forgot to deduct?

Three years, using an amended return (Form 1040-X). Worth filing if you have solid documentation for a year where you missed significant deductions — $2,000 in missed deductions at a 25% effective rate is $500 back in your pocket, which often covers the accountant’s fee to prepare it.

What about cash purchases at the lumber yard or supply house?

Cash is deductible just like any other payment — you just need the receipt. Ask for one every time. If you paid cash and lost the receipt, a written record of the purchase (amount, vendor, what you bought, what job it was for, and the date) created close in time to the purchase is better than nothing, but a receipt is always stronger.