Certification process
A hmrc document (tax residency etc.) is a UK public document, so it can go straight to the Foreign, Commonwealth & Development Office (FCDO) for the apostille certificate.
Document requirements
Original with wet-ink signature.
Digital e-Apostille
Possibly — an e-Apostille needs a PDF of your hmrc document (tax residency etc.) that has been electronically signed by a UK solicitor or notary public. If you only hold the paper version, you'll need the paper apostille.
The Hague Convention
An apostille authenticates a UK public document for use in countries that are members of the Hague Apostille Convention. Destinations outside the convention may need further embassy legalisation instead.