BIM45740 - Specific deductions - interest: On late paid tax, NIC and contract settlements
You should check the other guidance available on GOV.UK from HMRC as Brexit updates to those pages are being prioritised before manuals.
S34, S54 Income Tax (Trading and Other Income) Act 2005, S684(4) Income Tax (Earnings and Pensions) Act 2003, Sch1 Para6(4B) Social Security Contributions and Benefits Act 1992
Whether deductions are allowed for interest on late-paid tax and NIC depends on the kind of tax and NIC involved.
Interest on late paid Income Tax and Capital Gains Tax
Such interest is not deductible. See BIM42520.
Interest on late paid Corporation Tax