Job Costing Software for UK Workshops
Job costing is the practice of recording every cost attached to a single piece of work — parts, labour, subcontract, consumables — and comparing that total against what you charged for it. Job costing software does that recording as the work happens, rather than reconstructing it weeks later from a pile of paperwork.
For a workshop, the point isn't the accounting. It's that you can't price the next gearbox rebuild sensibly if you don't know what the last three actually cost you.
What Goes Into a Job Cost
Four categories, and workshops routinely capture only the first two properly.
- Parts — at cost to you, not at the price you charged. Both numbers need to be on the record.
- Labour — hours logged against the job, valued at your employment cost per hour, not your charge-out rate. Those are different numbers and mixing them is the most common costing error.
- Subcontract — chrome plating, machining, specialist testing, anything sent out.
- Consumables and sundries — welding gas, rags, cleaner, disposal, the fittings nobody writes down.
The fourth category is where estimates quietly go wrong. It's rarely huge on a single job, but it's systematic: it always runs one way.
A Worked Example
Take a hydraulic ram reseal. All figures below are illustrative — they're here to show the structure of the calculation, not to serve as industry benchmarks. Your rates will differ.
What the customer is charged (excluding VAT):
| Line | Amount |
|---|---|
| Seal kit | £68.00 |
| Hydraulic oil (5L) | £42.50 |
| Hoses (2) | £31.00 |
| Filter | £38.00 |
| Labour — 4.5 hrs @ £58.00/hr charge-out | £261.00 |
| Subcontract — chrome re-plating | £95.00 |
| Total charged | £535.50 |
What it cost the workshop:
| Line | Amount |
|---|---|
| Parts at trade cost (£41.00 + £26.00 + £18.50 + £24.00) | £109.50 |
| Labour — 4.5 hrs @ £24.00/hr employment cost | £108.00 |
| Subcontract at cost | £78.00 |
| Total cost | £295.50 |
Gross margin is £535.50 − £295.50 = £240.00, or 44.8% of the charged total.
That figure is only trustworthy if every line got recorded. Which brings us to the part that matters.
Where the Margin Actually Leaks
Take the same job and assume the filter went on the machine but never made it onto the card — someone grabbed it off the shelf mid-job and moved on.
You still bought the filter, so your cost stays at £295.50. But you never charged the £38.00, so revenue drops to £497.50. Margin falls to £202.00, or 40.6%.
One unlogged part, on one job, moved the margin 4.2 percentage points. Nothing about the work changed. The only difference was a record that didn't get made.
This is why job costing is a shop-floor data-capture problem before it's an accounting problem. The arithmetic is trivial. Getting the inputs is the hard part, and it fails at exactly one moment: when a technician has a part in one hand and something better to do than find a pen.
Why Most Job Costing Tools Miss Workshops
The established job costing products come from two directions, and both carry assumptions that don't hold on a workshop floor.
Accounting-derived tools treat the job as a cost code hanging off the ledger. They're strong on reporting and weak on capture — they assume someone will enter the data, and they don't much care who or when. In a workshop, "someone will enter it later" means it doesn't get entered.
Manufacturing and construction tools assume a job begins with a sales order or a priced quote, then track actual-versus-estimated against it. That's a genuinely good model when you know the scope up front. A reactive workshop frequently doesn't: the job starts as "hydraulics, no lift" and the scope emerges once the covers are off. Variance-against-estimate reporting is close to meaningless when there was never a meaningful estimate.
Neither is badly built. They're built for a different sequence of events.
What to Look For
- Parts logged at the machine, in seconds, from a phone. This is the whole ballgame. Every other feature is downstream of whether capture actually happens.
- Both numbers on every part — trade cost and charge price. A system holding only the sell price can't calculate margin at all.
- Labour at cost as well as charge-out. If the tool only knows your charge-out rate, its margin figures are fiction.
- Free-text lines. Workshops fit parts that aren't in any catalogue and send work to subcontractors who invoice on paper.
- Per-job margin visible without running a report. If checking a job's profitability takes a month-end export, nobody checks it, and pricing stays a guess.
- Costing that survives an open-ended job. Work stalls waiting on parts. The cost record has to tolerate a three-week gap without closing or nagging.
- A route into your accounts. The finished job should become a draft invoice in QuickBooks Online or Xero with the lines already populated.
Getting Started Without Buying Anything
You don't need software to start. You need the discipline, and software mostly exists to make the discipline survivable.
- Pick your ten most common job types.
- For the next month, record parts at trade cost and technician hours against each one — a spreadsheet is fine at this stage.
- Work out cost and margin per job using the structure above.
- Compare the result against what you assumed when you quoted.
It's common to find at least one job type you've been effectively subsidising, usually one where the labour runs long and the price was set years ago by habit. That single finding is normally worth more than the exercise costs.
Our workshop job costing calculator runs this calculation for a single job if you want to test the structure before committing to a month of record-keeping. For the manual route, the job tracking spreadsheet guide covers the columns worth setting up.
Frequently Asked Questions
What is job costing in accounting terms? It's the allocation of direct costs — materials, labour, and direct expenses — to an individual job rather than spreading them across a period. The output is a cost and a margin per job instead of only a business-wide profit figure.
How do you calculate job costing? Add parts at trade cost, labour at employment cost per hour, subcontract at cost, and consumables. Subtract that total from what you charged the customer excluding VAT. The result is gross margin in pounds; divide by the charged total for margin as a percentage.
Is job costing software different from construction job costing software? The construction variants add progress billing, retentions, and CIS handling, and they assume a priced contract at the start. The core calculation is identical — the difference is everything built around it.
Do I need to include VAT in job costing? No, if you're VAT-registered. Job costing works on figures excluding VAT, because VAT you charge isn't yours to keep. If you're not VAT-registered, there's no VAT to exclude in the first place. HMRC's guidance on VAT record-keeping covers what you need to retain separately.
The Short Version
- Four cost categories: parts at cost, labour at employment cost, subcontract, consumables. Most workshops miss the fourth.
- Charge-out rate is not employment cost. Mixing them produces margin figures that flatter you.
- Capture is the constraint, not calculation. One unlogged part moved a worked example 4.2 percentage points.
- Tools built for accounting assume someone enters data later. Tools built for construction assume a priced quote up front. Reactive workshops get neither.
- Start with ten job types and a month of honest recording before buying anything.
For the broader picture, job management software for UK workshops covers how these products differ by origin, and job logging software goes deeper on capturing parts and labour as the job runs.
Sources
This post covers job costing as a workshop practice and is not accounting or tax advice. The worked figures are illustrative. For record-keeping obligations, see HMRC's VAT record-keeping guidance, and check your own rates and treatment with your accountant.
We're building JobCardApp so the costing data captures itself — parts logged at trade cost and sell price from a phone at the machine, labour by technician, and per-job margin visible on the board without running a report. Join the waitlist for early access.
Last reviewed: 3 September 2026