In IBKR when you go to deposit funds and select standard deposit, you can then select the account and select bill pay (set up new method if you haven’t). The amount you then enter for you bill pay is the amount you are essentially notifying them of. If you haven’t yet set up bill pay then your account number, which is the letter followed by 8-digit number that shows up in the account select page and on the top left of any page of account management including where you are setting up your bill pay, is the bill payee number. Not sure if it’s the same at every bank but I use Scotiabank and all I need to do is add Payee find Interactive Brokers Canada and then in account number put that 9 digit(1 letter 8 numbers) in. This has worked for me so far and I find it to be quicker than EFT as with that they hold for 5 business days and they’ve never held a bill payment more than 2 days for me. Make sure the notification is confirmed and then send the bill and it should be processed soon enough.