HMRC now charging 6% interest fee for unpaid tax HMRC has increased the interest rate it charges on unpaid income tax, national insurance, capital gains tax, stamp duty, corporation tax and inheritance tax by 0.5 percentage points to 6% following last month’s Bank of England base rate rise. The rate now stands at a 14-year high and is more than double what it was last January, when it was 2.75%. However, those owed money by HMRC will receive just 2.5% interest, up by two percentage points since January last year. Of course many motorsport businesses suffer cash flow shortages during the close season and this happens to coincide with the payment of many tax bills. Motorsport businesses face particular challenges with cashflow at this time of year and will need to prioritise paying tax bills to avoid this expensive charge.