Guide · 6 min read
Parts, labor, inventory, sales tax, payroll — the financial system for mechanic shops.
Most shop owners watch revenue. The two numbers that actually matter: parts margin (should be 40–50%) and effective labor rate (billed hours ÷ paid hours × posted rate). Track those weekly and you'll see profit leaks instantly.
Different margin, different tax. Your bookkeeping system needs both as separate accounts.
Physical count of high-value parts monthly. Full count at year-end. Sloppy inventory = wrong COGS = wrong tax bill.
Parts taxable. Labor sometimes. Tires often have a separate disposal fee. Shop supplies sometimes. Your POS should handle it; check quarterly that it does.
Run W-2 payroll through a real provider (Gusto, ADP). Pay payroll tax on time. Late payroll tax is the IRS's #1 reason for shutting down small shops.
SnapBooks splits parts vs labor, tracks inventory, and keeps you on top of sales tax and payroll.
Start freeSeparately, always. Parts are COGS (and taxable in most states); labor is service revenue (taxability varies). Your POS or shop management software should split them on every invoice.
Depends on the state. Some states tax repair labor (TX, CT, NY in some cases), others don't (CA, FL, IL). Get this wrong and you owe years of back sales tax.
Physical count by Dec 31. Value at cost (FIFO or weighted-average). The difference between beginning and ending inventory + purchases = COGS.
Deductible operating expenses. Many shops charge a 'shop supply fee' on every invoice to recoup these — make sure that fee is taxable in your state.
Yes — liability is huge in auto repair (you're putting cars back on the road). LLC or S-corp protects personal assets. S-corp election once profits exceed ~$50K saves real SE tax.