14 CFR § 61.27

The holder of a certificate issued under this part may voluntarily surrender it for:

Cancellation;

Issuance of a lower grade certificate; or

Another certificate with specific ratings deleted.

Any request made under paragraph (a) of this section must include the following signed statement or its equivalent: “This request is made for my own reasons, with full knowledge that my (insert name of certificate or rating, as appropriate) may not be reissued to me unless I again pass the tests prescribed for its issuance.”