The SME scheme applies to companies who satisfy the requirements of the small and medium sized enterprise scheme.

The RDEC applies to any company that does not qualify for the SME scheme.

This includes companies who fail to meet the size requirements and therefore can only claim under the RDEC or companies who may have individual projects which do not qualify under the SME scheme if, for example, they are receiving certain grants or they have work subcontracted to them by a company that does not qualify under the SME scheme.

In the latter case, this means that a company that meets the size requirement but has projects that do not qualify can claim under both schemes.