Re: certificate of tax withholdings? / withholding certificate?
As far as I'm aware, in the UK we have no such thing as a "withholding certificate" or "certificate of tax withholdings". The problem with the names of legal or financial documents is that different documents exist in different countries, so translating their names doesn't always make sense.
If I told you that I will receive my "P60" in the post in the next few weeks, you would have no idea what I was talking about, but everyone in the UK would. It's the name of the form sent out at the end of each financial year, telling you how much you earnt in the last financial year and how much tax you paid.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.