Can API manufactures approval their product by mentioning USP/BP on COA. If their unit is not approved by USFDA and MHRA etc.
For Drug Substance - Active Pharmaceutical Ingredients:
Generally if you are looking at registering an API manufacturer in your medicinal product dossier, the manufacturing site would need a valid GMP certificate for that site. In addition the QP of the manufacturing site releasing the finished product will sign a declaration that the API is made in compliance with GMP.
The CoA is just a measure of testing and specification compliance with USP or Ph.Eur. This CoA is not enough to register an API in a drug product dossier. Information about the manufacture/ testing methods/ validation/ stability/ packaging of the API is required in the dossier and there are several ways to do this a) get a Certificate of Pharmaceutical suitability for the API from the EDQM, b) register a drug master file with the health authority then give a letter of access to your FP manufacturer which will be included in the drup product dossier together with the open part of the drug master file, c) include full details of Drug substance structure, manufacture, stability etc.
Excipients:
You just need confirmation that the excipient is USP, Ph.Eur. grade etc.
Hope this helps.