Account will be suspended within 60 days: VERIFICATION

I’m currently going through verification process and submitted a UTR and later a letter that came with a UTR. But Amazon sent me an email that “We need some additional documents to continue with your account verification. The UTR document you provided was not 1 of the acceptable document types.”
The email went on to say “If you do not upload this document within 60 days, we will be unable to prevent the suspension of your selling privileges.”

Now I’d like to know exactly what kind of document will be accepted by Amazon in this situation?
I trust you people here can be of assistance.

Thanks…