40 CFR 35.6235: Cost sharing.

A State must provide at least ten percent of the direct and indirect costs of all activities covered by the Core Program Cooperative Agreement. Indian Tribes are not required to share in the cost of Core Program activities. The State must provide its cost share with non-Federal funds or with Federal funds, authorized by statute to be used for matching purposes. Funds used for matching purposes under any other Federal grant or Cooperative Agreement cannot be used for matching purposes under a Core Program Cooperative Agreement. The State may provide its share using in-kind contributions if such contributions are provided for in the Cooperative Agreement. The State may not use CERCLA State credits to offset any part of its required match for Core Program Cooperative Agreements. (See § 35.6285 (c), (d), and (f) regarding credit, excess cash cost share contributions/over match, and advance match, respectively.)