It is your individual responsibility as a lender to ensure you track how much of your annual ISA subscription you have utilised, and how many ISAs you have opened per tax year. If you realise you have overpaid, report it to HM Revenue & Customs. You can do this by calling their ISA helpline on 0300 200 3300. If you do not spot the error, HMRC will make contact with you. HMRC will identify the payment that breached the limit. It will then start the process of "repairing" the ISA. All investments in the ISA that were made after the limit was breached will no longer be eligible for tax exemption. They will be handed back to the investor. An administration fee will be chargeable if you use more than your annual ISA allowance. If you attempt to make a deposit in your UOWN ISA account, of more than your annual ISA allowance, that entire sum will automatically be transferred to your UOWN standard lender account.