A variation is any change to the scope of work after the price is agreed — an addition, an omission, a substitution, or a change in how or when the work must be done. A client moving a wall, an architect upgrading a finish, a site instruction to work around another trade: all variations, all with a cost consequence, all changing what you are entitled to be paid.
The commercial rule is simple: the work changes when the paper changes. A variation priced and issued before (or as) the work is done is revenue. The same work done on a nod is a gift.
Why it matters
On fit-out and specialist contracting work, variations are routinely where the final margin is decided. The tendered price is competitive to the bone; the changes are not. A job that leaves site with its variations captured, priced and agreed can finish stronger than it was tendered. One that relies on reconstructing changes at final account finishes in an argument — and arguments about six-month-old verbal instructions are lost more often than won.
How it goes wrong
Never through ignorance — every site manager knows a change happened. It goes wrong because capturing it competes with twenty other jobs at 4pm on a Tuesday, and "I'll write it up later" quietly becomes free work. The fix is making the capture cheaper than the loss: raise it in a minute, price it from the same rates as the job, issue it, and let it roll into the account automatically.
In Vyntworks, client, internal and subcontractor variations each take about a minute to raise and track through to the final account. For the war stories, read the variations you forgot to charge for.