Keeping a project budget under control

Overruns almost never come from a bad initial estimate, but from what was added along the way.

Record every addition

Every "could we also" is a scope change. Keep a list with the cost, even if you decide to accept it. Without the list nobody can explain the overrun.

Work in phases

A phase with its own budget and its own result. That way you decide after each phase rather than finding out at the end.

Include a reserve

A percentage for the unforeseen, explicitly named. A budget without a reserve is a budget that will be exceeded.

Look weekly

Spend against progress, not against the calendar. A project at fifty per cent of budget and twenty per cent of the work is a problem visible in week three.

What to ask your supplier

A signal when an estimate starts slipping, not an invoice at the end. That is a matter of agreement, not goodwill.