September 30, 2026 · Mitt Patel · 6 min read
It's the third week of the month, and you're looking at a repair order for $1,100, with parts and labor lumped into one sales line and the supplier's core charge buried somewhere in parts cost. You know the shop made money on the job. You just can't say how much came from the labor and how much came from marking up the part.
Why the problem happens
Most shop management software is built to write a fast, clean invoice for the customer, not a clean set of books for you. Parts, labor, and core charges usually flow into QuickBooks as one deposit or one sales entry, because that's how the payment came in. It's simple at the counter. It's a headache everywhere else.
The cost shows up in decisions, not in any one invoice. If parts and labor share one income line, you can't tell whether your parts markup is actually covering your parts cost, or whether labor is quietly carrying the shop. You might raise labor rates when the real problem is parts pricing, or keep a supplier relationship that's costing you margin because you never see parts profit on its own.
Core charges add a second layer of confusion. A core is a deposit you pay when you buy a rebuilt part, refunded when you send the old part back. If that money isn't tracked separately, it sits inside your parts cost, making margins look worse than they are, or it disappears into your supplier balance, making it hard to know what you're actually owed.
Then there's inventory. Parts bought for a specific car on the lift and parts bought to sit on a shelf are different kinds of spending, but many shops expense them the same way. That means your profit for the month swings with how much you happened to buy, not with how much work you actually did.
None of this is a sign you're doing anything wrong. It's a sign the books need a structure that your shop software wasn't built to give you.
A worked example
Say your shop writes a repair order for $1,100: $700 in labor and $400 for a rebuilt alternator. Your supplier charged you $250 for the alternator plus a $100 core charge, refunded when you send back the old one you pulled off the car.
If all of that lands in one "sales" account, your books show $1,100 of income and $350 of parts cost, buried in one cost line. You can't see that the $400 in parts cost you $250, a $150 margin, while the $700 in labor cost you maybe $300 in technician pay, a $400 margin, for a combined margin of $550 on the job. Two very different stories, hidden inside one number.
Worse, the $100 core charge makes the alternator look like it cost $350, so its margin shrinks to $50. A few weeks later you return the old alternator and the supplier credits the $100. If that credit is logged as a reduction to parts expense, that month's parts cost looks artificially low, and you have no record of how many cores are still waiting to go back.
Split correctly, the same job tells you: labor income $700, parts income $400, parts cost $250, and $100 sitting in a core deposit account as money the supplier owes you once the old alternator goes back. When the credit arrives, it clears that account to zero. Your parts margin, labor margin, and outstanding cores are all visible at a glance, every month, without you having to reconstruct anything.
How to set it up
- Create separate income accounts for parts and labor. In your QuickBooks chart of accounts, set up "Parts income" and "Labor income" as distinct accounts under sales or income. If you sell tires, shop supplies, or sublet work like alignments, give those their own lines too.
- Map your shop software's categories to those accounts. Most shop management systems let you assign each invoice line item to a category before it syncs to QuickBooks. Take the time to map parts, labor, core charges, and any fees so they land in the right place automatically, instead of all hitting one sales account.
- Set up a cost of goods sold account for parts. Parts you buy to install on a repair order should post to a "Cost of parts sold" account, not to a general supplies or expense account. This is what lets you calculate parts margin instead of just parts spending.
- Open a core deposit account. Create this as a current asset (what you're owed), since a core deposit is money you paid to the supplier and expect back. When you buy a part with a core charge, that charge posts here, not to parts cost. When the credit comes back, it clears against the same account.
- Separate stock inventory from job-specific parts. If you keep parts on a shelf for common repairs, track those as inventory items in QuickBooks or your shop software. Parts ordered for one specific car on one specific repair order should be expensed directly to that job, not added to inventory.
- Reconcile monthly. Once a month, check that your parts income and labor income accounts match what your shop software reports for the same period, and that your core deposit account only holds cores you genuinely haven't returned yet.
The mistakes that undo it
- Letting the shop software do a generic sync. If you don't map categories deliberately, most systems default to dumping everything into one or two QuickBooks accounts. The setup only works if someone checks the mapping, not just the total.
- Posting core credits as a discount instead of clearing the core account. This makes parts cost look better than it is and hides how many cores are still outstanding.
- Expensing shelf stock the same way as job-specific parts. If a big stock order lands in the same month as a slow week for repairs, this makes profit swing for reasons that have nothing to do with the work you did.
- Skipping the quarterly parts count. Without a physical count, your inventory account on paper drifts from what's actually on the shelf, and neither number can be trusted.
- Changing the chart of accounts without telling whoever does your books. A new labor code or a new supplier with different core terms needs to be mapped in, or it'll land somewhere generic.
Monthly checklist
- Confirm parts income and labor income are posting to separate accounts, not one combined sales line.
- Check that parts cost of goods sold reflects what you actually paid for parts installed that month.
- Review the core deposit account balance and confirm it matches cores you're still waiting to return.
- Compare shop software reports for parts and labor totals against what landed in QuickBooks.
- Spot-check a few repair orders to make sure fees, sublet work, and supplies are mapped correctly.
- Once a quarter, do a physical count of shelf stock and adjust your inventory account to match.
Common questions
Do I need to track cores separately if my supplier automatically nets the credit against my next bill?
It helps to see the core account even so. Netting on the supplier's end doesn't tell you how many cores are sitting in your shop unreturned, which is money on the table until they go back.
What if my shop software won't let me split parts and labor by account?
Some systems export a single sales total by default but still track parts and labor internally. Check whether the export settings allow account mapping by category before assuming it isn't possible.
Should every part I keep on a shelf count as inventory, or just the expensive ones?
That depends on your shop. Some owners track only high-cost stock parts like alternators or starters and expense small items like filters and belts as used, though a careful bookkeeper would still want any shelf stock counted at least once a year. Either approach can work, but it should be a deliberate choice, not a default.
How often should I actually check parts margin versus labor margin?
Monthly is enough for most shops to catch a pricing problem before it costs much. If you're changing suppliers or labor rates, checking right after the change helps you see the effect quickly.
North Hudson Bookkeeping sets up this kind of chart of accounts for repair shops and keeps it current as your suppliers, software, and pricing change. The first call is free.
