Citizens Advice recommends obtaining written quotations and establishing the work and payment arrangements before appointment. [1]
Issue the same information
Give each bidder the same drawing revisions, specification and list of requirements. Record each clarification issued during pricing and share it with the other bidders. As a practical check, include a document-revision column in the comparison and ask every bidder to confirm the information used before you compare totals.
Ask bidders to identify departures from that information. An alternative material or construction method may be worth considering, but keep its price separate from the requested design until the design implications have been assessed. [2]
Build a comparison schedule
Use one row for each major package and separate rows for site management, access arrangements, temporary works, professional services, testing and handover. Ask bidders to mark each row included, excluded or provisional. Add a clarification column so an unanswered question remains visible instead of being mistaken for an included item.
For each offer, ask:
- What design and specification has been priced?
- Which items are excluded or supplied by the client?
- What provisional sums or product allowances remain?
- Are VAT and the basis of any later adjustment clear?
- What assumptions have been made about access, phasing and occupation?
Use these as comparison questions, and ask for a written answer wherever an offer is unclear.
Understand why prices differ
A contractor may have priced a different quantity, finish, construction sequence or risk allocation. RICS's cost-reporting guidance also distinguishes the original contract amount from instructed changes, provisional expenditure and other contractual adjustments. Investigate those differences before describing a gap as either a saving or overcharging. [3]
For an uncertain item, request the allowance, its pricing basis and the information needed to settle it. Ask each bidder to price your preferred specification where possible. Keep any unresolved difference flagged rather than inventing an adjustment yourself to make the totals look comparable.
Finish with an agreed scope
Create a clarification schedule and ask the preferred contractor to incorporate accepted answers into the contract documents. Note which options remain undecided and request decision dates. Before signing, check the revised offer against your comparison row by row and obtain an explanation for any answer that has changed.
Compare quotations using the same scope, specification and exclusions rather than applying a universal percentage difference between London quotes.