• Enquiry
• Quote
• Agree
• Work
• Invoice
• Paid

What a Written Variation Looks Like

Deciding to charge for an extra is the hard part. Recording it is the easy part, and it is the one most often skipped because it feels like paperwork for something that took ten minutes.

For a software-side reference alongside this discussion of pre-work decisions, contracts, and small-business administration, Monitask has this resource.

Four lines. Sent before the work. That is the whole mechanism.

The four lines

What was asked for. In the customer's terms, not yours — "the extra socket by the back door", not "additional 13A outlet, kitchen circuit".

What it will cost. A number, or a rate and an estimate of time where a number is not possible.

What it does to the timescale, if anything.

And that it is in addition to the original quote, named by reference.

Example: "Confirming the extra socket by the back door — £45 on top of quote 214. No change to the finish date. I'll do it Thursday with the rest."

Why before rather than after

Because after is a bill and before is an agreement.

A variation confirmed before the work can be declined. The customer reads £45, decides it is worth it or not, and either way nobody is surprised.

The same item on the final invoice is a query, and it is a query at the moment when the invoice most needs to be unqueryable.

The difference in effort is nil. The difference in outcome is the whole thing.

Where they go wrong

Sent and not acknowledged. A variation the customer never replied to is not agreed, and the ones that get contested are exactly the ones that were sent into silence.

Chase the reply. One line: "Just checking you're happy with the £45 before I do it."

Priced vaguely. "A bit extra" is not a price and will be interpreted at the low end.

Bundled. Three variations described together, with one total, cannot be partly disputed — which sounds convenient and is not, because a customer who disagrees with one will contest the whole.

And accumulated. Six variations sent at the end of the job, all at once, is a bill by another name and reads exactly as one.

The running total

On any job with more than two variations, keep a visible tally.

A short message every week or at each stage: "Variations so far: extra socket £45, moving the light £60. Running total on top of quote £105."

Nobody likes the number at the end to be a surprise, and the tally means it is not. It also gives the customer a natural moment to stop, which they may want and which preserves the relationship better than a large final figure.

Verbal variations that already happened

Confirm them the same day, in writing, even retrospectively.

"Following on from this morning — the extra socket we discussed, £45, I've noted it against the job."

Sent hours after the conversation, this is a contemporaneous record. Sent six weeks later with the invoice, it is an assertion.

The gap between those two positions is measured in hours, and it is the cheapest evidence available to a small firm.

When to do it for nothing anyway

When you have decided in advance that you will.

Some work should be free, and a variation record is still worth sending for it: "Sorted the loose handle while I was there — no charge."

That message does something a silent favour does not. It establishes that the item was outside the scope and that not charging was a decision, which means it does not become the baseline for the next request.

Where the customer proposes the variation in writing

Best case, and it happens more often than suppliers notice.

An email asking for something extra is half the record already. Reply to it rather than starting a new message, so the request and the price sit in one thread.

Confirm in the reply and do not change the subject line. A thread that runs request, price, acceptance is self-explanatory to anybody reading it later, including you.

Variations that reduce the job

These need recording too, and almost never are.

A customer who removes an item — decides against the second radiator, supplies their own materials — has changed the price downwards, and if that is not recorded the final invoice will show the original figure and produce exactly the dispute this page exists to prevent.

Send the same four lines with a minus sign. "Noting you're supplying the tiles — that takes £180 off quote 214."

It also buys credibility for the additions. A supplier who records reductions as carefully as increases is visibly running a process rather than looking for extras, and the additions are contested less often as a result.

Keeping them findable at invoicing

The variations only work if you can produce them when the invoice is queried.

One place per job. A folder, a thread, a note in whatever you use — the requirement is that a query six weeks later produces the record in under a minute rather than a search through a phone.

List them on the invoice individually, each with its date and its agreed price, rather than as a single line marked "extras". An itemised invoice is harder to query and the items are the ones you already have written confirmations for.

A customer who queries one item on an itemised invoice disputes forty-five pounds. A customer who queries a lump marked "extras — £320" disputes the lot, and the conversation starts from nothing.

The short version

• Four lines sent before the work: what was asked for, what it costs, what it does to the timescale, and that it is additional
• Before is an agreement that can be declined; after is a bill that becomes a query at the worst moment
• The effort is identical and the outcome is not
• Failures: sent without acknowledgement, priced vaguely, bundled so it cannot be partly disputed, or accumulated to the end
• Keep a running total on jobs with several variations, so the final figure is never a surprise
• Record the free ones too, so that not charging is visibly a decision rather than the new baseline

For broader background on pre-work decisions, contracts, and small-business administration, see Stripe.