Stamp Duty on AIB Mastercard being cancelled

Can anyone throw any light on this situation please. Son living abroad got statement dated 26th May 2012 saying 30€ due. It's a card he hasn't used for years. I paid it for him in cash at the post office on 6th June & he had signed the statement (that he had returned to me) & returned it to AIB. Got a letter for him dated 7th June 2012 saying - sorry you are cancelling the card etc. & confirming the account closed.
Got a statement dated 26th stating "previous balance 30€, interest 0.78, credit 15.00€ (by direct debit - which they don't say what account it's from & he doesn't know what account it is from either!), new balance €15.78 plus €0.03 interest. I ignored it thinking the details were just not up to date. Got another statement for him dated 26th July 2012, with the same details. There is another heading saying "Government stamp duty of €30 due 1st April annually and on date of closure". Does this mean that before he can have the account actually closed we have to pay another €15.81? If he/I doesn't pay it what will happen? I had thought stamp duty was payable in arrear not advance?

It is in arrears unless you're closing the account. So the €30 you paid on the 6th June would have been arrears for the year upto 31st May 2012. The new €30 would cover him until 31st May 2013.

If your son gets another credit card here in that time he should be able to use the letter of closure and not pay it again until it's due next year.

I'm not sure if that fully answers your question as I'm a little bit confused about the rest of the post. Did the original €30 pay off the previous stamp duty and then the mystery €15 paid half of the new stamp duty?

Thanks for the reply Oggster - what you are saying makes sense (at last!). The original €30 must have paid off the previous stamp duty & the €15 mystery d/d the new one. I think I'll get them to write to him in Australia direct & they can then tell him where the mystery d/d comes from!
Thanks again