There arent any tax offices these days, all done through the Post Office now.
From the V62 PDF -
What to do if you also need to tax your vehicle
If you do not have a V5C or the V5C/2 you will need to fill in this form and pay a fee. You can pay by cash, direct debit, debit card, credit card, cheque or postal order (made out to Post Office Ltd.), Post Office budget card or by traveller’s cheques (in pounds sterling).
If you are not the registered keeper of the vehicle you may not be able to tax until you get a V5C in your name.
https://www.gov.uk/government/uploads/sy...030815.pdf
From the V62 PDF -
What to do if you also need to tax your vehicle
If you do not have a V5C or the V5C/2 you will need to fill in this form and pay a fee. You can pay by cash, direct debit, debit card, credit card, cheque or postal order (made out to Post Office Ltd.), Post Office budget card or by traveller’s cheques (in pounds sterling).
If you are not the registered keeper of the vehicle you may not be able to tax until you get a V5C in your name.
https://www.gov.uk/government/uploads/sy...030815.pdf