The difference between an estimate versus the final bill is normal. Handled badly it is the single most common source of disputes in trade and repair work. Handled well it is a two-line explanation nobody argues with.
Get the approval before the cost
The rule is simple and almost always ignored under time pressure: approval comes before the work, not before the invoice.
The moment you know the figure will move, stop and tell them. A phone call, followed by a message so it is in writing:
Lifted the floor this morning. Two joists are rotten and need replacing before the new boards go down. That is about 34,000 more than the estimate, taking it to roughly 265,000. Happy to proceed on that basis?
Thirty seconds, and the invoice becomes uncontroversial.
What “approval” means
In writing, from someone allowed to spend the money. A text message is fine. A nod from whoever happened to be on site is not, particularly on commercial work where the person present may have no authority at all.
If you set a tolerance in the estimate, movements inside it do not need a fresh approval. That is what the tolerance is for. Above it, you promised to ask, so ask.
Showing the difference on the invoice
Do not hide it and do not make the customer reconcile two documents in their head. Reference the estimate and show the variance as its own line.
Description Amount
Bathroom re-fit per estimate EST-0117 231,000
Additional: replace two rotten joists, approved
by text 14 August 34,000
Subtotal 265,000The approval is named in the line. Anyone reading it later, including someone who was not there, can follow it.
When the job comes in under
Say so. An invoice lower than the estimate, with a line explaining why, buys more goodwill than almost anything else you can do.
Re-pipe not required; existing pipework reusable.
Estimated 385,000, invoiced 322,000.Customers remember that. It is also the strongest argument that your estimates are honest, which makes the next one easier to accept.
When they dispute it
Three documents settle most disputes: the estimate with its assumptions, the approval message, and the invoice showing the variance. If you have all three, the conversation is short.
If you are missing the middle one, you are arguing about what was said. That is the situation worth building your process to avoid.
Repeated overruns
If your estimates are consistently 20% under, the problem is the estimating, not the customer. Common causes worth checking:
- Pricing the work but not the access, clearing up, or waste.
- Optimistic labour hours, especially for the last 10% of a job.
- Not pricing the return visit you always end up making.
Track the gap on a few jobs. If it is consistent, adjust the rate rather than repeatedly asking for approvals.
The paper trail
Keep the estimate, the approval and the invoice together. Nothing here is stored for you, so save the sheets to your own disk as you go.
Writing the approval request
The message doing the work is short. Four things, in this order:
- What you found.
- What it means for the job.
- What it costs, and the new total.
- A direct question.
Opened up the wall this morning. The cabling is older than expected and does not meet current standard, so it needs replacing before the new sockets go in. That is about 18,000 more, taking the job to roughly 142,000. Shall I go ahead?
No apology, no padding. A number and a question. Most customers say yes, and the ones who do not have told you before you spent the money.
Keeping it out of the invoice
The best outcome is an invoice that needs no explanation because every variance was agreed as it happened.
That is worth optimising for. A customer who has approved three small additions during the job reads the final invoice as confirmation. A customer meeting all three for the first time on the bill reads it as a surprise, and reacts accordingly.
Next
For getting the estimate right first time, see how to write an estimate. For a template with a tolerance already in it, see an estimate template you can reuse. If the scope firms up, send a quote instead.