Garage parts inventory: billing parts and labour on the job card

In a garage, the job card consumes parts from stock, carries the labour lines and becomes the final bill. A worked example in rupees, plus common mistakes.

Last reviewed: November 2026

In a garage that also does repair work, the job card is the document that uses up your stock. Every part issued to a vehicle is deducted against its job card, every labour operation is added as a separate line, and when the work is done the job card becomes the final bill. If you keep that one rule, parts stock and billing stay in step. If parts leave the store any other way, they drift apart.

Why is the job card the consumption document?

A spare parts counter sells across the counter: one sale, one stock deduction. A workshop is different. Parts leave the store over hours or days, go into a vehicle, and get billed only when the customer collects it. The job card is the only record that is open for that whole period.

So treat it the way a shop treats a sales invoice. A part does not leave the store without a job card number against it. That gives you three things together:

Stock accuracy. On-hand drops when the part is issued, not days later at billing.
Complete bills. Every part issued shows up on the customer's bill. Fitted parts that never get billed are a quiet loss in many workshops.
Accountability. You can see which job, which vehicle and which mechanic used each part.

What goes on a job card?

A job card that works as both a consumption record and a bill has four parts:

Header: job card number, date opened, customer name and phone, vehicle registration, make and model, odometer reading, and the complaint in the customer's own words.
Parts lines: part number, description, quantity issued, rate. Each line deducts stock.
Labour lines: operation description, fixed rate or hours × hourly rate. These are services and never touch stock.
Close-out: returns of unused parts, the final total, and conversion to a tax invoice.

Keep parts and labour as separate lines from the start. Mixing them into one "service charge" makes the bill hard for the customer to check and the stock impossible to reconcile. It also causes trouble on the invoice, where they usually have to be shown separately.

Can you show a job card example in rupees?

Here is an illustrative job card for a routine service with a brake repair on a hatchback. All figures are illustrative only, and tax is left out on purpose (see the GST section below).

Job card JC-0412 · Vehicle: hatchback, petrol · Complaint: due for service, noise when braking

Line	Type	Description	Qty / Hours	Rate (₹)	Amount (₹)
1	Part	Engine oil, 3.5 L pack	1	1,450	1,450
2	Part	Oil filter	1	220	220
3	Part	Air filter	1	380	380
4	Part	Front brake pad set	1	1,600	1,600
5	Part	Brake cleaner spray	1	240	240
6	Labour	Periodic service (fixed rate)	1	900	900
7	Labour	Front brake pad replacement	1.5 hrs	400	600
8	Labour	Wheel alignment	1	500	500
		Parts subtotal			3,890
		Labour subtotal			2,000
		Total before tax			5,890

What happens to stock: lines 1 to 5 each reduce on-hand the moment the storekeeper issues them against JC-0412. Lines 6 to 8 do not touch stock at all.

Now suppose the mechanic was issued two brake cleaner sprays but used one. The second goes back as a return against JC-0412. Stock goes up by one, and line 5 stays at quantity 1. The bill and the shelf agree.

How should the parts flow work day to day?

A simple sequence that holds up in a busy workshop:

Open the job card at vehicle intake, with an estimate the customer approves.
Issue parts against the job card from the store. No job card number, no issue.
Add labour lines as operations are done, or at the start for fixed-rate jobs.
Return unused parts against the same job card before closing it.
Check additional work. If the mechanic finds something new, add it to the job card only after the customer approves the revised estimate.
Close and invoice. The closed job card converts into the tax invoice, with parts and labour as separate lines.

Consumables such as cleaner sprays, cotton waste and grease are the grey area. Either issue them per job like parts, or expense them as workshop consumables and recover them through a flat charge. Pick one method and use it every time. Doing both will double-count.

What about GST on the bill?

The final invoice has to meet the normal GST invoice requirements: supplier and customer details, invoice number and date, description, HSN or SAC, taxable value and tax shown properly. Our guide to GST invoice format requirements covers the fields.

This post does not cover how parts and labour are taxed, including whether they carry different rates or whether the job counts as a composite supply. That depends on how you structure and bill the work and on current rules. Confirm it with your CA or on the official GST portal before you set up your billing. Whatever they advise, keeping parts and labour on separate lines from the job card onward makes that advice easy to apply.

Common mistakes that throw garage stock out

Issuing parts "for now" without a job card. The part is fitted, the card is never updated, and the part is never billed.
Deducting stock only at billing. Vehicles waiting for parts or approval hold fitted parts that still show as available.
Unrecorded returns. Parts go back on the shelf with no entry, so stock looks higher than the books say, or the customer is billed for a part they did not get.
Labour set up as a stock item. Some systems allow it. It creates negative or meaningless stock and muddles reports.
Mixing parts into a lump-sum labour charge. The customer cannot check the bill, and you cannot see which parts are actually moving.
No reorder levels on fast movers. Oil, filters and brake pads go out daily. Set reorder points so a routine service never waits for a part. The reorder point formula works the same way here.

When does this not apply?

If you only sell parts across the counter, a normal sales invoice is your consumption document and you do not need job cards. If you only do labour and the customer brings their own parts, you have no parts stock to track. Record the customer's parts on the job card for reference only, with no stock entry. Larger workshops handling insurance claims or warranty jobs will need extra fields and approvals beyond what is described here.

What should software do for a workshop?

At minimum: job cards that deduct stock on issue, returns against the same card, separate labour lines that never touch stock, conversion of a closed card into a GST invoice, and reports of parts consumed by job, vehicle or mechanic. If you are comparing options, our guide to choosing inventory software in India gives a checklist. If you are still on spreadsheets, Excel vs inventory software explains where spreadsheets break down for a workshop.

FAQ

Should parts be deducted from stock when issued or when the bill is made? Deduct when the part is issued to the job card. That is when it physically leaves the store. If you wait for the final bill, any vehicle that stays in the bay for days shows parts as in stock when they are already fitted. That leads to false availability and double-promising the same part to two customers.

What happens to a part that was issued but not used? Return it against the same job card so the stock comes back in and the line comes off the bill. Do not just put it back on the shelf without an entry. An unrecorded return shows up later as a stock excess you cannot explain. It also hides a habit of issuing parts the mechanic did not need.

How do I bill labour that is not a fixed-price job? Record labour as its own line with a clear description and either a fixed rate for a standard operation or hours multiplied by your hourly rate. Agree the basis with the customer on the estimate before work starts. Keep labour lines out of the parts stock completely, because labour is a service and has no stock to deduct.

Is GST charged the same way on parts and labour? Do not assume it is. Parts and labour can be treated differently, and the classification and rate depend on how the supply is structured and on current notifications. Show parts and labour as separate lines on the invoice. For the treatment that applies to your garage, confirm with your CA or the official GST portal.