If you miss the deadline for filing your self-assessment tax return (31 January for online filing) you will be charged a £100 penalty.
If the return is filed more than three months late, an additional £10 per day is charged, and after six months another penalty is imposed as the higher of £300 or 5% of the tax due. The flat-rate penalties will stand even if the tax return shows no tax.
Your company’s Corporation Tax return is due a year after the end of the accounting period. The penalty for being even one day late is £100 and another £100 is imposed after three months, then 10% of the tax due if the return is six months late. If you make a habit of submitting late company returns, the fixed penalties rise to £500 each time.
The penalties for paying VAT late can amount to up to 15% of the delayed payment, for even one day late.
Pay attention to any electronic warning notices from HMRC about penalties due. If you have a ‘reasonable excuse’ you may escape the penalty, but lack of funds is generally not an acceptable reason.