Have requested this three times without any issue (I have not attempted yet to reduce it - however it is always marked as a capital overpayment on my mortgage statement). Generally I word it something like this:
I want to make a fixed monthly capital overpayment without changing the term of my mortgage in addition to my regular mortgage payment, from dd/mm/yyyy until further notice in the following amount: €xxx.
Please confirm this in writing.
Regards,
...
I funnily enough actually have the last response from UB with me here so I have transcribed it below:
"You contacted us to increase the monthly step-up payment on your mortgage account.
We've done that for you now. Your increased step up of €xxx will start on dd Month yyyy.
If you regularly overpay your mortgage, we credit your account immediately and the overpayment will reduce the balance, but not the term, of your mortgage. It will also have the effect of adjusting your interest.
If we change your rate, your normal monthly repayment will change automatically, but any regular overpayment you have in place will remain the same unless you ask us to change it.
If you have any questions...
If you feel you may have difficulty ..."