39 CFR 501.20: Discontinued Postage Evidencing Indicia.

(a) Decertified indicia (evidence of pre-paid postage) are indicia that have been withdrawn by the Postal Service as valid forms of postage evidence through publication by the Postal Service in the Federal Register, or by voluntary withdrawal undertaken by the provider.

(b) Effective December 31, 2024 all Postage Evidencing Systems that do not to produce Intelligent Mail Indicia (IMI) for evidence of pre-paid postage must be withdrawn from service. Non-IMI indicia, which are not compliant with the then-current version of the IMI-PC, will be decertified and may not be used as a valid form of postage evidence. These decertified indicia may not be recognized as valid postage for use or refunds, after June 30, 2025.