Post-job costing for tradespeople: 15 minutes that improve your next quote

Most master tradespeople know exactly what they quoted on a job. Fewer know what the job actually ended up costing. Post-job costing is what closes that gap - and it is also the cheapest form of training you can give your estimating.

What is post-job costing?

Post-job costing means comparing your quote - the pre-job calculation - with the actual figures once the job is finished. How many hours were spent compared with what you allowed for? What did the materials cost compared with the calculation? Were there items you had not included at all? The result is a variance in kroner and per cent, and a concrete list of where your next calculation needs adjusting. Work in amounts excluding VAT throughout - the 25% VAT simply passes in and out and says nothing about how the job went.

Why do most people skip it?

The answer is almost always time. Once a job is handed over, the next one is waiting, and sitting down with receipts and timesheets feels like admin that does not send invoices. The trouble is that without post-job costing you repeat the same skewed assumptions in quote after quote. You only spot the problem in the annual accounts, and by then you can no longer see which jobs dragged you down - or why.

A 15-minute routine per job

You need neither spreadsheets with macros nor a bookkeeper. Set aside a quarter of an hour once the invoice has been sent:

• Dig out the quote and note the calculated hours and material amounts
• Pull the actual hours from the timesheets or your time tracking
• Gather the material invoices from the wholesaler for the job
• Work out the variance in kroner and per cent - hours and materials separately
• Briefly note the cause: what had you not seen coming?

Five steps, a quarter of an hour. Put the figures into the same simple sheet every time, so you can compare across jobs. Do it consistently and after a month you will have a picture of your estimating that very few of your competitors have of theirs - and that picture is what sharpens your next quote.

A worked example: quote versus reality

A carpenter quotes DKK 80,000 excluding VAT for a roof terrace. The pre-job calculation allows for materials of DKK 30,000 and 100 hours at DKK 300 in cost price, i.e. DKK 30,000 in labour - DKK 60,000 in variable costs in total and an expected contribution margin of 80,000 - 60,000 = DKK 20,000. Once the job is finished, the post-job costing shows: materials of DKK 31,200 and 112 hours at DKK 300 = DKK 33,600, DKK 64,800 in total. The actual contribution margin is 80,000 - 64,800 = DKK 15,200. The variance is 20,000 - 15,200 = DKK 4,800, equivalent to 24% less contribution margin than calculated. Note the split: materials drifted only 4% (DKK 1,200), while the hours drifted 12% (12 hours, DKK 3,600). That is an entirely typical picture.

What you typically discover

After five to ten post-job costings, the patterns emerge. Hours almost always drift more than materials - materials come with an invoice, while hours include setup, driving, waiting time and just one more thing, which rarely appear in the calculation. Then there are the standing forgotten items: waste disposal, consumables, equipment hire and the final walkthrough with the customer. It is rarely one big mistake that costs you. It is the same three or four small items missing every time.

Feed the lessons into your next quote

Post-job costing is only worth anything if it changes your next pre-job calculation. If hours consistently drift 10-15% on a particular type of work, build that into the hours going forward - not as a hidden buffer on the price, but as a real figure. If you always forget waste disposal, make it a standing item in every quote. And update your material prices when the wholesaler does. If you use a quoting tool like Calco, where you describe the job and get a calculation with real wholesaler prices, you can put your own experience figures in, so every new quote starts from what reality has taught you.