194 Bids, Tenders and Proposals problem of inflation exists. Commercial banks may be able to act as an authoritative source of reference in these situations. The financial part of your bid should emphasize the need for an eventual contract to include a mechanism that takes account of cost escalation. Matters such as the applicability of withholding taxes and the provisions of double taxation agreements will need to be covered in the terms of a draft contract at the stage of negotiation. The extent to which it may be advisable to address these points in your price information will depend on the particular circum- stances of the contract. Payment The tender documents may define the schedule on which payments will be made to the contractor. On fixed-price contracts, payments are normally linked to the submission and approval by the client of agreed deliverables and the achievement of performance targets or project milestones. On relatively short time-based contracts, invoices are normally submitted immediately on completion of the work, in the case of assignments of less than one month's duration, or at regular intervals in arrears, eg on the last working day of