48 CFR §43.203

1. (a)Contractors' accounting systems are seldom designed to segregate the costs of performing changed work. Therefore, before prospective contractors submit offers, the contracting officer should advise them of the possible need to revise their accounting procedures to comply with the cost segregation requirements of the Change Order Accounting clause at 52.243-6.
2. (b)The following categories of direct costs normally are segregable and accountable under the terms of the Change Order Accounting clause:
   1. (1)Nonrecurring costs (e.g., engineering costs and costs of obsolete or reperformed work).
   2. (2)Costs of added distinct work caused by the change order (e.g., new subcontract work, new prototypes, or new retrofit or backfit kits).
   3. (3)Costs of recurring work (e.g., labor and material costs).