scopeeconomics
Find missing scope and duplicated allowances, then explain the movement.
A spreadsheet can calculate correctly and still describe the wrong project. Start a review with scope boundaries, source revisions and package interfaces. Then check quantities, units and rate build-ups. Reconcile the assembled estimate after the individual packages have been examined.
Give the reviewer enough evidence to challenge the method. A lump sum allowance may be reasonable, but its work content and basis should be visible. Where evidence is weak, record that limitation rather than creating a false impression of precision.
Shared access, testing, temporary works and mobilisation often sit at package boundaries. Ask who owns each item and where it appears in the model. A supplier return may include something that the estimator has also priced separately. Removing the duplicate requires a scope check, not simply reducing the more expensive line.
Compare successive issues on a consistent basis. Separate scope, quantity, rate and other movements so that a reader can understand why the total changed. Keep the sign convention clear. A reduction in the price does not establish that risk has reduced or that the scope is complete.
A review action needs an owner, a required response and a consequence for issue. Some findings can be closed immediately. Others require a qualification or further information. Make that status visible to the person authorising the estimate.
Practise explaining the correction in words as well as numbers. For example: “The access allowance is included in the trade return and duplicated in preliminaries. Subject to confirming the same scope and duration, remove the second allowance.” The qualification matters because two similar descriptions can cover different obligations.
An estimate totals £180,000. A £12,000 access allowance is included in both the accepted trade quotation and preliminaries. The reviewer confirms that both entries cover exactly the same work and duration.
Original review exercise. The negative value represents a deduction, not a separate cost saving from a changed method.