A job finishes. The invoice goes out. You still cannot tell whether the labour, materials and subcontractors left any profit. The practical answer to “what is job costing?” starts with that gap.
Job costing assigns revenue and costs to a defined job, then compares the finished result with the original cost budget and quote. Done properly, it starts before you price the work. It ends only after every charge, credit and time entry has landed.
What is job costing in a trade business?
Job costing treats each piece of work as its own financial unit. A customer. A site. A scope. A job number.
Every estimate, quote, work order, time entry, purchase, approved change, supplier credit and invoice carries that reference. You can then see what you expected to spend, what you committed to spend and what you actually spent.
The basic calculation is:
Job cost = direct labour + materials + subcontractors + equipment + other direct costs + allocated overhead
Your policy decides which costs sit in each bucket. Write that policy down. If the estimator treats vehicle costs as overhead but the bookkeeper charges them directly to jobs, your reports will not agree.
Job costing compared with averaging repeated work
Job costing follows distinct work. A bathroom renovation, boiler replacement, roof repair, pest treatment or commercial repaint can each become a separate job.
Averaging is different. It combines the costs of repeated or standardised production and spreads them across units. That may suit identical items produced under controlled conditions. It hides too much on field work where access, site condition, travel, customer changes and crew hours differ.
Do not average away a bad site. Give the work its own number and record what happened.
What does job order costing mean?
Job order costing is another name for assigning costs to individual orders or jobs. In a trade business, the order might be a service visit, repair, installation, maintenance contract visit or defined stage of a larger project.
The important word is individual. You are not asking whether the business had a good month. You are asking whether this job recovered its costs and produced the result built into its price.
An HVAC business managing service and installation work can give a unit replacement its own job number. Technician time, installed equipment and fittings, equipment hire and an electrical subcontractor’s invoice all carry that number.
A garden installation can carry a different job number. Crew time, plants, soil, hired equipment and waste charges follow that job from purchase to close-out.
Check local requirements before costing the job
Licences, permits, tax treatment, contracts and worker cover can affect whether you may perform the work and which costs belong in the budget. Check each question with the body responsible for it. Do not rely on an old job folder.
Put job-specific permits, inspections, certificates and compliance work against the job. Treat recurring business registration and licence costs under your documented overhead policy. Do not dump an annual business cost into whichever job happens to be open.
United States
Ask your state contractor licensing board which contractor license covers the work. Ask your state or city electrical, plumbing or mechanical licensing office which trade license the person performing it needs.
Ask the local building department whether the job needs a permit or inspection. Ask your secretary of state about business registration. Check EIN and federal tax questions with the IRS (opens in a new tab).
Put known job-specific permit, inspection and compliance costs into the estimate. Do not hide them inside an unexplained allowance.
United Kingdom
For gas work, check who may perform it with the Gas Safe Register (opens in a new tab). For self-certification of notifiable electrical work under Part P in England and Wales, use the government list of competent person schemes (opens in a new tab).
For water fittings compliance, ask the water undertaker or enforcing authority responsible for the site. Start with the official government service for England (opens in a new tab), Wales (opens in a new tab), Scotland (opens in a new tab) or Northern Ireland (opens in a new tab) and follow its current route to the responsible authority.
Ask building control (opens in a new tab) about building regulations approval, or check building standards in Scotland (opens in a new tab). Check self assessment, VAT and CIS questions with HMRC (opens in a new tab). Ask Companies House (opens in a new tab) about limited-company requirements.
Record job-specific approval and compliance work in the scope. Keep recurring company, registration and licence costs in the overhead policy.
Canada
Ask your provincial or territorial trade licensing and safety authority about trade licences and trade permits. Ask the municipality about a business licence or building permit.
Ask your provincial or territorial business registry about business names and registration. Check business number and GST/HST questions with the Canada Revenue Agency (opens in a new tab). Ask the provincial or territorial workers' compensation board about coverage for workers.
Add required job-specific permits and inspections to the correct job. Handle recurring business licence and registration costs through the written overhead policy.
Australia
Ask your state or territory licensing regulator which trade or contractor licence covers the work. Use the same regulator for questions about home building contracts within its scope.
Check ABN, GST and BAS questions with the Australian Taxation Office (opens in a new tab). Ask ASIC (opens in a new tab) about company and business-name registration. Ask your state's workers' compensation insurer or regulator about cover for workers.
Put job-specific permits, inspections and contract administration into the scope and cost budget. Treat recurring company registration and trade licence costs under the documented overhead policy.
The seven steps involved in job costing
If someone on the crew asks what is job costing in practice, show them this chain. Each step creates the record needed by the next one.
Step 1 — Define the job and inspect the site
You cannot cost a job that has no boundary. Define the work before building the budget.
Record:
- Customer and site.
- Job number and responsible person.
- Requested outcome.
- Included labour and materials.
- Assumptions about access and site condition.
- Exclusions.
- Customer-supplied items.
- Required approvals, inspections or certificates.
- The point at which the job will be treated as complete.
Inspect the site before quoting when access or existing conditions could change the work. Open the ceiling hatch. Check the switchboard. Find the isolation point. Measure the route. Photograph what will be covered later.
Do not force unrelated work into a broad job because it belongs to the same customer. Separate it when the scope has a different approval, crew, completion date or profit result.
Keep the work together when the tasks form the same promised outcome and separating them would create paperwork without improving control. The boundary should help you price, run and review the work.
If the customer later asks for work outside that boundary, keep it connected to the original job but record it as an approved change. Do not silently rewrite the original scope.
Step 2 — Build the cost budget
Estimate labour, materials, subcontractors, equipment, other direct costs and overhead under your written policy. Keep each bucket separate.
Record the quantities, hours and assumptions behind the amounts. A total with no build-up is hard to correct later.
Use a direct-cost test. If the cost arose because you took this job and you can trace it to the job, charge it directly. If it supports the business across many jobs, handle it through the overhead policy.
#### Direct labour
Direct labour is the cost of time spent delivering the job. Every entry needs the worker, date, hours, activity and job number.
A technician who works across several jobs must split the day between those job numbers. A timesheet showing only the day cannot tell you which job used the labour.
Decide what your labour cost includes. Employer-paid labour costs can include wages, payroll taxes or contributions, leave, pension or superannuation, and worker cover when your policy includes them in labour burden. Write down the included items so estimators and bookkeepers use the same figure. Keep non-job time separate rather than pushing it into whichever job was open that day.
#### Materials
Charge installed materials to the job that used them. Include stock withdrawn from the store, not just purchases made for a named site.
When a supplier invoice covers several jobs, split its lines across those jobs. Do not assign the full invoice to the first job number you recognise.
Record delivery and other job-specific material costs under your written policy. Record unused material returned to stock. Apply a supplier return or credit to the job that carried the original purchase.
A purchase does not always equal consumption. Track what went to site, what was installed, what came back and what was left with the customer.
#### Subcontractors
Record the subcontractor's agreed amount as a committed cost when you place the order. Replace or reconcile it with the actual cost when the invoice arrives.
Match the invoice to the subcontracted scope. If the subcontractor completed approved extra work, connect that charge to the corresponding customer approval.
Do not close the job because the subcontractor has finished on site. Wait for the invoice or confirm the final subcontractor charge.
#### Equipment and other direct costs
Charge hired equipment to the job that required it. Do the same for job-specific disposal, permits, specialist testing and travel that your policy treats as direct.
Separate owned equipment from hired equipment. If an owned vehicle or machine serves many jobs, recover it through a consistent usage charge or the overhead policy. If you charge its use directly to a job, do not recover the same cost again through overhead.
#### Overhead
Overhead covers costs that support the business but cannot be traced cleanly to a job. Office and admin costs, recurring business licences and general business insurance usually belong here. A permit, insurance extension or compliance cost bought only for one job is direct.
Decide whether you recover overhead through a consistent job allocation, through your pricing policy or through another documented method. The main rule is simple: count it once.
If office costs are included in an overhead allocation against the job, do not add the same office costs again when reviewing profit. Keep direct costs direct. Moving a clearly traceable hire charge into overhead makes the job look cheaper than it was.
#### Estimated, committed and actual costs
Keep these figures in separate columns:
- Estimated cost is the budget prepared before work.
- Committed cost is an order or obligation not yet fully invoiced.
- Actual cost is the charge already recorded.
An unfinished job can look profitable when supplier and subcontractor commitments are missing. Review actual costs plus open commitments before deciding whether the remaining budget is safe.
Step 3 — Set the price and issue the quote
An estimate tests likely cost and price before you set the quoted price. Record the assumptions behind it. A range with no scope notes is not useful when the site differs from what you expected.
Keep the estimated cost by bucket. Labour should not be buried beside materials and subcontractors. You will need those separate figures when the job closes.
Choose either a markup rule or a target-margin rule and use the matching formula. Applying a target margin as though it were markup understates the price.
The quote sets the price and scope. State what you will supply, what you will do, what you will not do and how approved extra work will be handled.
Learning how to write a quote with clear scope and exclusions matters to job costing because a vague quote gives you nothing reliable to compare against. Put the job number on the quote and retain the cost budget used to build its price.
A quote is not proof of profit. It is the starting promise. The field records show what it took to deliver that promise.
#### Calculate job cost, markup and margin
Add the costs assigned under your written rules. Then use the correct formula for pricing or reviewing the job.
Price = cost × (1 + markup)
Price = cost ÷ (1 − target margin)
Markup = profit ÷ cost
Margin = profit ÷ selling price
The profit from that comparison is not automatically business net profit. It depends on which direct costs and overhead your written job-cost policy includes and which business costs sit outside it.
Markup and margin are not interchangeable. Markup describes what you add to cost. Margin describes the profit left as a share of the selling price.
Use the profit margin calculator with your own job figures when checking the difference.
#### Oak Street worked example
Oak Street is the house electrical example. All figures below are sample currency units, not prices or a rate card.
R. Chen's job at 14 Oak Street covered a bathroom exhaust fan, 150mm and ducted through the roof, plus four LED downlights. Estimate E-1847 showed a range of 900–1,400. Quote Q-1847 was 1,105.
The measured job cost against that original quote was 850. The original quoted work therefore produced:
1,105 − 850 = 255 profit
The margin was:
255 ÷ 1,105 ≈ 23%
The markup was:
255 ÷ 850 = 30%
The ceiling was lined, and the quote excluded chasing. Extra cable and chasing were approved on site as a 160 change. That is a change order in the United States and Canada, or a variation in the United Kingdom and Australia. Invoice INV-1847 was 1,265.
Do not calculate profit by subtracting the 850 cost from the 1,265 invoice. The cost of delivering the 160 approved change is not given. Combining that revenue with the original job cost would invent a profit figure.
Keep the added revenue and added cost visible. When the change cost is known, review it separately and as part of the final job. Until then, the defensible calculation is the original 1,105 quote against the stated 850 job cost.
Step 4 — Open the work order
Use the same job number. Give the crew the approved scope, site details, tasks, exclusions and cost-recording instructions.
What is a work order? It is the operational instruction for the crew. It should show the job number, site, scope, exclusions, tasks, required materials, site notes and approval status.
Do not make the crew interpret the customer quote on site. Give them the practical details they need to perform the work and report costs. For US contractors, this guide to keeping the work order, crew and invoice aligned explains that hand-off in local terms.
Make responsibility clear. Name who records labour, stock withdrawals, purchases, subcontractor work and site changes.
Step 5 — Capture costs as the work happens
Assign every time entry and direct cost to a job. Record commitments when orders are placed, not only when invoices arrive.
Field records are strongest at the point of work. By the end of the week, the extra fitting, spare cable and extra trip have blurred together.
Put the job number on:
- Time entries.
- Purchase orders and receipts.
- Supplier invoice notes.
- Stock withdrawals and returns.
- Subcontractor orders.
- Equipment hire.
- Site photographs and field notes.
- Approved changes.
Give each record an owner. The technician records time and stock used. The person ordering materials adds the job number. The office splits supplier invoices and follows up missing credits.
If a receipt covers several sites, mark each line before it reaches bookkeeping. If material moves from one job to another, transfer the cost instead of leaving it where it was first ordered.
Unassigned labour belongs in a holding list for immediate review, not in a random open job. Ask the worker where the time went while the day is still fresh.
A supplier invoice without job references must be split from the order, receipt or site notes. Do not accept the supplier total as a job cost without checking which sites used the items.
Mobile field records can help the crew attach time, notes and photographs while still on site. After setting the cost buckets and recording rules, review the mobile tools for field records.
Step 6 — Stop and record changed scope
When site conditions or customer instructions change the scope, stop. Describe the extra work, set the added price or pricing method, note any effect on the work, get approval, record it under the original job number, then continue.
In the United States and Canada, the approved record is a change order. In the United Kingdom and Australia, it is a variation.
This protects the original estimate. You can see whether the quoted scope performed as expected and whether the approved change covered its own cost.
For US contractors, how to write a change order before extra work starts sets out the document hand-off in local terms.
Extra work completed without approval needs management attention. An invoice line written afterwards does not repair the missing agreement.
Step 7 — Reconcile, close and use the result
The invoice should follow completed quoted work and approved changes. It should not introduce surprise work that the customer never saw in writing.
Match the invoice back to the quote, work order and approvals. That closes the revenue side. It does not close the job cost until all costs and credits are recorded.
Use a hard close-out gate. Confirm that quoted work plus approved changes agrees with invoiced revenue. Confirm that all labour, supplier charges, subcontractor invoices, equipment costs, returns and credits are posted. Clear every open commitment before relying on the result.
Compare estimated, committed and actual cost by bucket. Start with the largest difference, then read the field records behind it.
Ask a concrete question:
- Did labour hours exceed the estimate because the production plan was wrong?
- Did hidden site conditions change the scope?
- Were materials wasted, returned or charged to the wrong job?
- Did a supplier price or subcontractor commitment differ from the budget?
- Was approved extra work recorded without its matching cost or revenue?
- Was overhead counted twice?
Separate a scope miss from a production miss. A scope miss means the quote failed to include required work. A production miss means the scope was understood but took more resources than planned. The fix is different.
If overhead appears twice, choose a recovery method and correct the policy. If different people use different cost buckets, publish a short list and make every document follow it.
Do not turn an unusual job into a new rate card. Correct the specific assumption, quantity, labour allowance, exclusion or field instruction that failed. Use clean job records to refine recurring work.
Common questions
How often should open jobs be reviewed?
Review them often enough to act before the budget is spent. Set the review point from the work stage and purchasing activity, then check actual cost plus open commitments rather than actual invoices alone.
Where should rework be recorded?
Keep rework against the job that caused it, with a clear note explaining why it happened. Do not move it to overhead just to protect the job result. The true cost tells you whether the fault came from scope, workmanship, materials or supervision.
Should every service call get a job number?
Give a service call its own job number when it has a distinct customer, site and scope. That is what makes the answer to “what is job costing?” useful on small work as well as larger installations.
How should shared travel time be assigned?
Use one written method and apply it consistently. Assign traceable travel to the jobs that caused it, or recover shared travel through overhead, but do not count the same time in both places.
Open the next estimate and correct that input before another quote leaves.