Bill of quantities

What it means

A bill of quantities is a list of all the work and materials needed for a construction project, with quantities and units, such as cubic metres of concrete, square metres of plaster or the number of windows. It is based on the design documents and forms the basis for pricing the project.

The bill of quantities serves as the basis for the construction budget, for comparing contractors' bids and for invoicing work actually done. In a tender, all bidders receive the same bill of quantities to price, so their bids can be compared item by item.

There is an unpriced bill, which contains only items and quantities, and a priced bill, in which the contractor adds a unit price and total for each item. The priced bill of quantities often becomes an annex to the contract for work.

How it works in practice

Construction work is often invoiced on the basis of a statement of work done that follows the items in the bill of quantities. The construction supervisor or the client's technical supervisor checks that the work was actually carried out to the stated extent before the invoice is approved for payment.

If actual quantities turn out to differ from the bill during construction, additional or reduced work arises. The contract should set out how such changes are priced and approved, for example using unit prices from the priced bill, to avoid disputes.

Construction work between VAT payers is often subject to the domestic reverse charge. When invoicing from a bill of quantities, it must therefore be determined correctly which items fall under this regime, and the invoice must say so.

What to watch out for

An incomplete or inaccurate bill of quantities leads to an underestimated budget and later price increases. When commissioning construction, it is important that the bill is prepared by an experienced quantity surveyor and matches the current design documents.

Contractors sometimes deliberately underprice items where they expect lower quantities and overprice those where they expect more. When comparing bids, it is worth looking not only at the total price but also at the unit prices of key items.