Three kinds of income
Split revenue into parts, labor and sublet, which is work sent to another shop such as machine work or alignments. Each has a different margin. Labor margin is often the strongest, and parts margin depends on your markup. Your shop management software produces a daily or monthly summary; post that summary in the accounting file rather than each repair order.
Cost of parts and core charges
Parts bought for repair orders are cost of goods. Suppliers may charge a core deposit that is refunded when you return the old part. Track cores as a receivable from the supplier, not as an expense. Returns and credits should be matched to the original invoice. Reconcile the supplier statement monthly, because shops often pay duplicates or miss credits.
Shop supplies, tools and environmental costs
Rags, cleaners, fluids and small hardware are shop supplies, and many shops charge a fee to customers. Record that fee as income and the supplies as an expense. Hazardous waste disposal, tire disposal and fluid recycling are regular costs that need their own lines. Technician tools are sometimes owned by the technician, so decide in writing who buys what.
Technician pay and efficiency
Technicians may be paid hourly, flat rate, or on commission. Flat-rate pay can create payroll complications such as overtime and minimum wage calculations, so ask a payroll specialist or attorney about the current rules. Track billed hours versus paid hours to measure efficiency. If you pay for ten hours but bill only seven, the missing three need an explanation.
Work in progress, warranty and customer credit
At month end, repairs that are partly done may have costs recorded without matching revenue. Understand how much is in progress so the profit and loss is not distorted. Warranty work paid by manufacturers or parts suppliers should be recorded separately to see claim rates and recoveries. If you offer in-house credit to customers, track balances and follow up on them regularly. Credit card fees, state inspection or sales tax requirements, and insurance claim payments from body work deserve a quick check with the relevant agencies. Insurance payments for body shops may be split between the carrier and the customer's deductible, so record both parts against the same job.
Key numbers to review monthly
A few ratios tell you whether the shop is healthy: gross profit on parts, gross profit on labor, average repair order value, car count, and the share of work that is repeat business. Compare the shop's effective labor rate with the posted rate, because discounts and unbilled time wear it down. Add comebacks, meaning repairs redone at no charge, as a tracked cost. A rise in comebacks points to training, parts quality or diagnosis problems.
Most shops buy from several suppliers on open accounts. Reconcile each statement to your records and pay on terms. Disputed invoices, returns not credited and double billing are common, and they cost real money when no one checks.
Worked example with numbers
A repair order totals $1,000 before tax: $600 of parts at retail, $400 of labor. The shop paid $380 for the parts and $240 for the technician's time on this job. Gross profit is $1,000 - $380 - $240 = $380, a 38% margin. Parts alone earned $600 - $380 = $220 (about 37%), and labor earned $400 - $240 = $160 (40%).
Now add a $45 shop supplies fee charged to the customer and about $30 of actual rags and fluids used. Record the fee as income and the supplies as expense, and the job nets $15 more. If you had never tracked these, you would not know whether the fee covers the cost.
Mistakes that cost money
Expensing parts when they are bought instead of tracking them against repair orders makes monthly margins swing wildly. Treating core deposits as expenses instead of receivables from the supplier loses refunds. Not recording warranty work separately hides jobs that paid nothing. Giving discounts off the posted labor rate without tracking them makes the effective rate drift below target without anyone noticing. Customer vehicles on the lot are never your assets.
Check your work
Compare your shop software's monthly sales and parts cost reports to the books. Gross profit on parts and on labor should match within a small, explained difference.
Common questions
Should I charge sales tax on labor?
It depends on the state and the service. Check with the state tax agency or a CPA.
How do I track a customer who leaves the car unpaid?
Keep the repair order and the storage terms. An attorney can explain your lien rights.
This guide is general information, not tax, legal or accounting advice. Rules, fees and due dates change; check with the IRS, the NJ Division of Taxation or a licensed professional for your situation.