Turning an estimate into a bill of quantities that foots

Updated: 2026-08-13 · ISKRIT

The schedule you bill against and the estimate you priced are the same list of work seen twice. When they are typed separately, they drift, and the first person to notice is the one rejecting your application for payment.

Built, not retyped

An estimate already contains every item, its quantity, its unit and its value. A schedule built from those lines sums to the contract by construction: there is no arithmetic to get wrong, because the total was never recomputed. A schedule retyped into a blank grid has to be reconciled by hand every time the contract changes, and it usually is not.

The three things that break in the retyping

The rounding case is the one that causes the most argument for the least money. Values rounded to whole currency units on 180 lines can leave the total short, and a reviewer who checks the sum before the substance stops there.

Grouping

Items are grouped the way the work is run and inspected, not the way the estimate happened to be assembled. Grouping by section or by structure lets a reviewer walk the site and tick lines in order; grouping by supplier or by the order the estimator thought of them does not. The grouping is also what makes partial certification possible, since an owner can certify a completed section while another is still in dispute.

The check before anything is billed

One arithmetic test catches most rejected applications: does the schedule sum to the contract sum, including approved variations. If it does not, no percentage complete is worth computing yet. Running that check automatically, and refusing to issue the certificate until it passes, removes the single most common reason for a rejected draw.

Variations belong in the schedule

An approved variation that is billed as a separate invoice sits outside the schedule, so the schedule no longer describes the contract and the running totals no longer reconcile. Adding the variation as lines in the schedule and adjusting the contract sum keeps one document as the record of what was agreed.

The bill of quantities generator builds the schedule from estimate lines with units normalised and duplicates merged, and the work completion certificate tool checks the schedule against the contract sum before it issues anything.