By Paul Emanuelli

This article is an excerpt from The Art of Tendering: A Global Due Diligence Guide, which is available for purchase.

The World Bank’s Guidelines: Selection and Employment of Consultants by World Bank Borrowers (referred to as the World Bank’s Guidelines) recognize that institutions have a broad range of different contract pricing structures to draw from for the procurement of consulting services. For example, the World Bank’s Guidelines recognize these structures:

  • the Lump Sum Contract, where the requirements are clearly defined;
  • the Time-Based Contract, where it is difficult to define the scope and length of the assignment;
  • the Retainer and/or Contingency (Success) Fee Contract, where remuneration is contingent on a successful transaction and expressed as a percentage of the transaction price;
  • the Percentage Contract, which is a percentage of the project costs; and
  • the Indefinite Delivery Contract, for specialized on-call services provided over an indefinite period of time.

Some excerpts describing the various contract payment structures recognized by the World Bank’s Guidelines are set out below:

World Bank
Guidelines: Selection and Employment of Consultants by World Bank Borrowers
Types of Contracts
4.1 Lump Sum Contract. Lump sum contracts are used mainly for assignments in which the content and the duration of the services and the required output of the consultants are clearly defined. They are widely used for simple planning and feasibility studies, environmental studies, detailed design of standard or common structures, preparation of data processing systems, and so forth. Payments are linked to outputs (deliverables), such as reports, drawings, bills of quantities, bidding documents, and software programs. Lump sum contracts are easy to administer because payments are due on clearly specified outputs.
4.2 Time-Based Contract. This type of contract is appropriate when it is difficult to define the scope and the length of services, either because the services are related to activities by others for which the completion period may vary, or because the input of the consultants required to attain the objectives of the assignment is difficult to assess. This type of contract is widely used for complex studies, supervision of construction, advisory services, and most training assignments. Payments are based on agreed hourly, daily, weekly, or monthly rates for staff (who are normally named in the contract) and on reimbursable items using actual expenses and/or agreed unit prices. The rates for staff include salary, social costs, overhead, fee (or profit), and, where appropriate, special allowances. This type of contract shall include a maximum amount of total payments to be made to the consultants. This ceiling amount should include a contingency allowance for unforeseen work and duration, and provision for price adjustments, where appropriate. Time-based contracts need to be closely monitored and administered by the client to ensure that the assignment is progressing satisfactorily and that payments claimed by the consultants are appropriate.
4.3 Retainer and/or Contingency (Success) Fee Contract. Retainer and contingency fee contracts are widely used when consultants (banks or financial firms) are preparing companies for sales or mergers of firms, notably in privatization operations. The remuneration of the consultant includes a retainer and a success fee, the latter being normally expressed as a percentage of the sale price of the assets.
4.4 Percentage Contract. These contracts are commonly used for architectural services. They may be also used for procurement and inspection agents. Percentage contracts directly relate the fees paid to the consultant to the estimated or actual project construction cost, or the cost of the goods procured or inspected. The contracts are negotiated on the basis of market norms for the services and/or estimated staff-month costs for the services, or competitively bid. It should be borne in mind that in the case of architectural or engineering services, percentage contracts implicitly lack incentive for economic design and are hence discouraged. Therefore, the use of such a contract for architectural services is recommended only if it is based on a fixed target cost and covers precisely defined services (for example, not works supervision).
4.5 Indefinite Delivery Contract (Price Agreement). These contracts are used when Borrowers need to have “on call” specialized services to provide advice on a particular activity, the extent and timing of which cannot be defined in advance. These are commonly used to retain “advisers” for implementation of complex projects (for example, dam panel), expert adjudicators for dispute resolution panels, institutional reforms, procurement advice, technical troubleshooting, and so forth, normally for a period of a year or more. The Borrower and the firm agree on the unit rates to be paid for the experts, and payments are made on the basis of the time actually used.