Practical completion is the point at which the work is finished for its intended use, even though a few minor defects or small items may still be outstanding. The bathroom can be used, the deck can be walked on, the shop can open. It is a term from building contracts, and the contract usually defines it, but the idea applies to any job big enough to have stages. A great deal hangs on the date. It typically triggers the final progress payment, the release of part of any retention, the start of the defects liability period, the handover of keys and responsibility for the site, and often the point at which the client's insurance takes over from yours.
The question in every dispute about practical completion is whether what is left undone is minor. A missing towel rail is minor. A shower that leaks is not. Defining in advance what complete means for your kind of work, and agreeing on a short list of what is outstanding at handover, takes most of the heat out of it.
In practice
A renovator finishes a $24,000 bathroom with 10 per cent, $2,400, due at practical completion. At the walk-through the owner finds a chipped wall tile behind the door and a towel rail that is loose. Everything else works and the room is in use. The renovator and the owner sign a one-page handover note: practical completion reached on that day, two items on the defects list, both to be fixed within ten working days. The final payment falls due, and any disagreement is now about two small jobs rather than about whether the whole bathroom is finished.
Without that note, the same two items can be used to hold back the whole $2,400 for weeks. With it, the dates and the list are in writing, signed by both.
For small jobs with no formal contract, the same habit works in miniature: finish, walk through with the customer, write down anything outstanding and when it will be done, and invoice the same day. The guide to deposits and progress payments covers where completion fits in the payment stages.