TFC60600 | Penalties: maximum amount of penalty for making a prohibited payment
From HM Revenue & Customs · Tax-Free Childcare Technical Manual
Childcare Payments Act 2014, section 45(6)
The maximum amount of a penalty issued as a result of making or permitting prohibited payments is 25% of the repayable top-up element that has been assessed under section 41 of the Act (see TFC55100).
For example, if the prohibited payment was £500 (of which £100 was the top-up element), the penalty would be £25.