Subject: Re: IBKR question
I really think the problem was that I bought the bought just a few minutes after converting GBP into USD and though the increased USD amount was shown nevertheless the currency exchange still was not settled, because next day I received this email:

Currency Conversion Notification
This is to inform you that Interactive Brokers executed a currency conversion in your account U****.... either because a negative cash position is not allowed in this account type or the negative cash position was caused by a recurring investment trade.

ACTION SYMBOL EXCHANGE QTY PRICE CURRENCY DATE/TIME
Sold GBP.USD FXSETTLE ..... 1.35 USD 2025-08-28 14:06:34 EDT

In order to protect our clients and the firm, it is IBKR's policy to cover negative cash positions in non-compliant portfolios, as specified in the IBKR Customer Agreement and on the IBKR website.

If you wish to avoid automatic currency conversions in the future, you may perform your own conversions on any of IBKR's trading platforms. Instructions for converting currency (FX Orders) on IBKR platforms can be found in our User Guides.

Btw: I do not have a cash account, but by purpose a pure cash account.