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HMRC internal manual

Compliance Handbook

Penalties for Failure to Pay on Time: Rules for specific taxes: Annual Tax on Enveloped Dwellings (ATED): Penalties: Failure to pay all or part of amounts due - initial penalty

A person incurs an initial penalty when they do not pay Annual Tax on Enveloped Dwellings (ATED) by the penalty date, see CH155410.

The amount of the initial penalty is 5% of the amount unpaid at the penalty date.

See the example at CH155470.