Yes, IBKR can accept CHAPS (same-day UK payments) transfers for GBP currency.
Create a deposit notification from Client Portal by selecting the Transfer & Pay menu followed by Transfer Funds and then Deposit Funds. Once there, select British Pound (GBP) as the currency and Bank Wire as the method.
The cut-off time to submit instructions for same-day payments is 3:30pm UK time. If you set up the payment after the cut-off time, on a weekend or on a public holiday, the payment should arrive the next working day.
For details on the procedure in Client Portal, see How do I transfer funds to IBKR?
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