Once the winning supplier (based on the evaluation criteria) has been identified and the department has concluded all negotiations the department can proceed with the purchase. The department and the supplier should sign the contract in accordance with delegated authorised signatories as detailed in the Financial Regulations (section 1.5).
Note: remember that any advance payment in excess of £50,000 (excl. VAT) can only be made following receipt of an Irrevocable Banker's Guarantee (DOC).