2 CFR § 200.405 - Allocable costs.
(a) A cost is allocable to a particular Federal award or other cost objective if the goods or services involved are chargeable or assignable to that Federal award or cost objective in accordance with relative benefits received. This standard is met if the cost:
(1) Is incurred specifically for the Federal award;
(b) All activities which benefit from the non-Federal entity's indirect (F&A) cost, including unallowable activities and donated services by the non-Federal entity or third parties, will receive an appropriate allocation of indirect costs.
(c) Any cost allocable to a particular Federal award under the principles provided for in this part may not be charged to other Federal awards to overcome fund deficiencies, to avoid restrictions imposed by Federal statutes, regulations, or terms and conditions of the Federal awards, or for other reasons. However, this prohibition would not preclude the non-Federal entity from shifting costs that are allowable under two or more Federal awards in accordance with existing Federal statutes, regulations, or the terms and conditions of the Federal awards.
(d) Direct cost allocation principles: If a cost benefits two or more projects or activities in proportions that can be determined without undue effort or cost, the cost must be allocated to the projects based on the proportional benefit. If a cost benefits two or more projects or activities in proportions that cannot be determined because of the interrelationship of the work involved, then, notwithstanding paragraph (c) of this section, the costs may be allocated or transferred to benefitted projects on any reasonable documented basis. Where the purchase of equipment or other capital asset is specifically authorized under a Federal award, the costs are assignable to the Federal award regardless of the use that may be made of the equipment or other capital asset involved when no longer needed for the purpose for which it was originally required. See also §§ 200.310 through 200.316 and 200.439.
(e) If the contract is subject to CAS, costs must be allocated to the contract pursuant to the Cost Accounting Standards. To the extent that CAS is applicable, the allocation of costs in accordance with CAS takes precedence over the allocation provisions in this part.