It depends on the form, and on the old authority the surveyor owes the contractor no duty: where the form makes the bill a contract document and corrects errors, as JCT 2011 With Quantities does, the contractor does not carry the error, but where it does not the contractor bears the risk, and held that a quantity surveyor employed by the employer owes the contractor no duty for errors in the bill

It depends on the form, and on the old authority the surveyor owes the contractor no duty. Where the form makes the bill a contract document and provides for errors to be corrected, as JCT 2011 With Quantities does, the contractor does not carry the error: in Co-operative Insurance Society v Henry Boot an error in the bill was corrected and treated as a variation, so the contractor was paid for the consequent work. Where the form has no such provision, the contractor bears the risk, and obvious items such as floorboards must be priced even if omitted from the bill, as Williams v Fitzmaurice shows. As against the surveyor, held that a quantity surveyor engaged by the employer, having no contract with the contractor, owes it nothing in respect of errors in the bill. Those cases are old, and since Hedley Byrne v Heller it is arguable that a surveyor who knows the contractor relies on the bill could owe a duty of care, but the point is untested.