A bill of quantities is a document used in tendering in the construction industry in which materials, parts, and labor (and their costs) are itemized.
[1] The bill of quantities is issued to tenderers for them to prepare a price for carrying out the construction work.
"[2] The practice historically of estimating building costs in this way arose from non-contractual measurements, taken off drawings to assist tenderers in quoting lump sum prices.
The first refers to a specific item, e.g., "additional alterations to services when installing said shower unit", where an item for alterations to existing services is not contained within the bill of quantities but some work is envisaged.
The second type of sum is where money can be allocated to any item, within the bill of quantities, in the same way as the above example or used as "additional work to be undertaken by the contractor, at the request of the contract administrator".