Mid-build changes feel small — move an outlet, upgrade a tile, shift a wall. Individually minor, collectively fatal. The fix isn't refusing changes; it's logging them where you can see the total.
Rules that protect your budget
Never approve verbally. A change without a written price is an unpriced invoice waiting for the end of the job.
Log every change separately — date, description, cost impact, schedule days. Approved changes add to forecast; proposed ones are decision pressure.
Watch the running total. "$780 of approved changes" is information; discovering them at final invoice is a surprise.
Tie changes to the payment schedule. A change order on a stage you already paid for is a negotiation you already lost.
What "separate" means
The original contract price stays fixed in your records. Changes live in their own ledger — approved, proposed, rejected — so you can always answer "what did we agree to, and what did it add?"