Extras arrive one line at a time, spread over weeks, and surprise you at the final invoice. This log adds them up, guards the 10 percent line, and asks the one question that decides most disputes: is it agreed in writing? Free, no account; everything stays on your device.
At the final invoice, memory is the weakest evidence in the room. A dated log with amounts and yes-or-no on written agreement turns "I never agreed that" into a ten-second lookup. Your extras also count automatically in the budget tracker, so your real total is always one glance away. If the extras are becoming the project, read why quotes differ: thin quotes and extras are the same problem in two chapters.
A log for extras and variations: every added cost recorded with its amount and whether it was agreed in writing, with a warning when the total passes the usual 10% contingency.
What you enter: Extras with amounts and their written-agreement status; optionally your contract sum. What you get: A current extras overview with totals, shared automatically with the budget tracker. Everything stays on your device.
Around 10 percent of the contract sum is a common contingency for genuine surprises: what is found behind a wall or under a floor. Much more than that usually means the original quote was priced thin, or changes are being agreed too casually. The log above warns you the moment you cross 10 percent.
An extra (or variation) is work outside the agreed scope: discovered rot, a moved soil pipe, extra sockets you asked for mid-build. Changing your mind about something already agreed is a variation you requested, and you pay for it; work the builder should reasonably have foreseen and priced is a discussion, not an automatic bill.
Insist on it, every time, before the work is done. A text message or email with a description and a price is enough. Verbal extras are where final-invoice disputes come from, and by then the work is in your wall and your negotiating position is gone.
Ask for an itemised breakdown, compare it against your own log, and pay the undisputed part while you query the rest in writing. Under the Consumer Rights Act 2015 a price that was never agreed must be reasonable; you do not have to accept any number that appears at the end.