I am with AIB and this is the procedure for me. Firstly, I am presuming that you want to reduce the term of the mortgage using the 9k as opposed to just reducing the monthly payment.
1. Go to branch and pay cash/cq/transfer to your mortgage account
2. Send a fax to the mortgage dept stating your account number, sort code, address etc stating that you wish to pay 9k against your capital and reduce the term of the mortgage. Repeat this by stating that you wish your monthly payments to remain the same at X (give your payment amount). Confirm this again by asking the bank to advise you in writing of your new termination date of your mortgage.
3. Make sure the fax is signed by all account holders
4. Check your next mortgage payment to make sure they have not done the opposite of what you requested.
Within a week, you should receive a letter acknowledging receipt of your 9k and advising a new end date of your mortgage.
Every jan you should receive a cert of interest. However if you have internet access to your mortgage you can keep a better eye on whats happening.
Hope this helps.