Need niyo po iparegister yung pos machine( hardware + software) but no need to get accreditation on your part, basta mag submit ka lang sa BIR ng requirements pwede mo idownload sa BIR website (search mo RMC 5-2021), may checklist po don. I think kailangan lang pumirma ng sworn statement ng client (Annex A-1 - system is used and maintained by client) and comply with the checklist.
And most importantly, kailangan i enroll nung client yung machine sa BIR ESales for monthly reporting ng gross sales, malaki penalty pag di ito na comply.