Bill of Quantities, Variations and Stage Billing Explained

Each line of a bill of quantities carries an item number, a description, a unit such as cubic metre, square metre or each, a quantity and a rate. Quantity times rate gives the line amount, lines roll up into sections, and the sections add up to the contract sum.

Read the preamble too. It states how work is measured and what the rate includes, so a line for brickwork may already cover scaffolding or may not. Many site arguments start from a rate that someone assumed would cover something it never did, such as hoisting, curing or making good after the plumber.

Treat the BOQ as the reference point. Every later change hangs off it.

A variation is any change to the contracted scope, whether extra work, omitted work or a change in specification, and the client or consultant issues an instruction in writing. Without it you build at your own risk.

Price a variation using contract rates where an item matches, a negotiated rate where it does not, or day-work records for small tasks such as breaking out a slab. Number every variation, state its effect on cost and mark it approved, pending or rejected, so the register reads at a glance for anyone on site.

Pending variations are the most dangerous. Work gets built while approval is still a phone call away, and the argument over who agreed to what arrives at final account stage, when memories have changed.

Stage billing claims only new work. The quantity surveyor or site engineer measures what has been built, in the same units as the BOQ, and records it against each item. The sheet shows cumulative quantity to date and previous quantity for every item, and the difference between the two is this period’s claim.

Add materials on site if the contract allows it, subtract retention held back, and show approved variations as their own block. The client then sees at once what is original scope and what was added after signing, without hunting through emails or site instructions.

Sign the measurement sheet with the client’s representative before the bill goes out, because an unsigned sheet gives the certifier room to dispute every quantity. No signature, no bill.

The certificate is the consultant’s or client’s confirmation of the amount payable, so match each stage bill to its certificate number and compare the figures line by line. Gaps show reduced quantities and refused items.

Track each certificate through its life, from submitted to certified, invoiced, paid or part paid, and note any amount withheld and the reason. When the final account arrives, every adjustment and its reason will already sit in one trail that the quantity surveyor can follow from start to finish.

This link also protects cash flow. A bill with no certificate is a request, not an entitlement, and a request can sit unpaid for as long as the client likes.

Excel works for a single small project. With several sites, the same item gets copied across files, a variation lands in one workbook but not another, and someone bills the old quantity. A project record holding BOQ lines, variations, measurements, bills and certificates as linked entries removes the re-typing, and the errors that re-typing breeds fall with it.

Test any setup with one question: pick a certificate and trace it back to the measured quantity and the original BOQ line. More than a minute means the chain is broken.

Try that trace today. Use your oldest live project.