The short answer, explained
HMRC does have a power to recover tax debts directly from your bank or building society account, known as direct recovery of debts, but it's used sparingly and only after other attempts to collect have failed.
It's designed for cases where the debt isn't disputed, you have the funds available, and you've repeatedly ignored HMRC's attempts to contact you about paying.
Before using the power, HMRC must leave a minimum amount in your account untouched and give you formal notice, so this isn't something that happens without warning.

