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How to Automate Parts-to-Invoice Workflows in Your Repair Shop

You can stop revenue leakage by linking job cards directly to parts usage and invoices so every part used on a job is automatically added to the customer invoice. StockPRO does this by tracking parts issued to a job and pushing them into the invoice with one workflow, eliminating manual re-entry and missed line items.

In this article

  • Why repair shops lose money on parts (and how much)
  • How to track mechanic labor on the invoice from the job card
  • The best way to prevent parts being used but not billed
  • Step-by-step: from shelf to job to invoice

Why do repair shops lose money on parts?

Shops often use parts from the shelf for a job but never add them to the invoice. By the time the job is done, the technician forgets exactly what was used, or the office staff don't have a clear list. The result: 10–15% of revenue walks out the door unbilled. Automating the path from parts issued → job card → invoice fixes this.

Typical revenue loss from unbilled parts (industry estimates)

The real cost It's not just the cost of the part—it's the lost margin. Every unbilled part is revenue you'll never see. Multiply by hundreds of jobs a year and the number is substantial. Automation pays for itself many times over.

How do I track mechanic labor on an invoice?

Labor and parts must both flow from the job card to the invoice. Use a system where labor types and hours are on the job card, and when you convert the job to an invoice, both labor lines and parts lines are pulled in. StockPRO's automotive parts and industrial equipment workflows support job cards with labor and parts, so you get one accurate invoice with no manual retyping.

One job card → one invoice: labor and parts
On the job card On the invoice
Labor type, hours, rate Labor line items (no re-entry)
Parts issued to job Parts line items (auto-added)
Subcontractor / outwork Pass-through line items

What's the best way to prevent parts from being used but not billed?

Issue parts only against a job card. When parts are "issued to job," they're reserved and linked to that job. At invoice time, the system can add those parts as line items automatically. Nothing gets used without a job, and no job gets closed without those parts appearing on the invoice.

Issue parts to the job only No part leaves the shelf without being issued to a job. The job card is the only way to "consume" parts.
Complete labor and parts on the job Technicians (or parts staff) add every part used. Labor is recorded on the same job card.
Convert job to invoice One action pulls all labor and parts onto the invoice. No retyping, no guessing.
Review and send Office reviews the auto-populated invoice and sends. Revenue matches what was done.
Multi-branch tip For multi-branch setups, use the same rule at every location. See our guide on scaling a multi-branch service center so every branch follows the same parts-to-invoice process.

Automating parts-to-invoice isn't just about software—it's about making sure every part that leaves the shelf is tied to a job and then to an invoice. That's how you turn hidden leakage into visible revenue.

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