Something to watch out for if you are paying HMRC electronically.
HMRC do not use 'faster payment' which means that an electronic payment to HMRC takes 3 or 4 days to clear, and this needs to be factored in if you are making a payment by bank transfer. With electronic payment now mandatory on some taxes, and interest and penalties for late payment for others, this is a key point to bear in mind.
If you pay by Direct Debit then the same considerations are not a worry as HMRC debit your account at the appropriate date, likewise if you pay via HMRC's online bill payment service using a debit card the payment will be with them immediately. The problem is with BACS type payments. It is worth remembering that late CIS/PAYE payments now attract penalties from the second default of any tax year onwards.