Why is my account showing a negative cash balance after adding money?
When you add money to your account with a debit card, you can use that money to invest immediately. Debit card payments don’t appear in your cash balance for 1-2 working days, so if you do decide to invest straight away your account will temporarily show a negative balance.
Please be assured this isn't anything to be concerned about, it will correct itself once we receive the payment from your bank.
The important figure to pay attention to when dealing is the 'Amount available to invest' rather than the total cash figure displayed for the account.