1. When you pay tax to the government, you are the tax payer and the government is the taxing authority (please correct me if I am wrong.). If you work for a company, the company (the employer) deducts your income tax from your pay checks (collects the tax) and remits it to the government. In a similar case, a retailer collects the sales tax and remits it to the government. What do you call the employer or the retailer in terms of tax?
2. In an imagined scenario, you have paid the tax and for whatever reason you need proof that you have done it. You go to the government center and ask one of the staff member there to give you proof. He checks your records and prints out something like "Deel Tax Payment Certificate", stating you have paid the tax. In general and formal terms, what do you call the person who helped you? Could that be "the handling person"?

Thank you guys in advance. Any suggestions would be greatly appreciated.

Hi Grammar Geek! Thank you so much for doing the research for me. That's very nice of you. BTW, I like your avatar.

Withholding entity sounds great to me. It is much better than those I have thought of so far.

Agent is one I can use. I was thinking about the word but just not quite sure. How about official or officer? Which one sounds better to you? "The person who assisted me" is a good one but I wish it were in a short form.

Thank you, Grammar Geek. Actually there isn't a sentense. It's a form. I am trying to translate a form in Chinese into English. It looks like:

Name of Tax Payer:
Taxable Amount: $5,000
Actual Tax Payment: $500
Date of Tax Payment: 06/14/2005
Taxing Authority:
Withholding Entity:
Name of Agent: Mary Lee
Signiture of Agent: X___________

Above is the translation.