Calculating a UK tax return is on the face of it very simple. You read through the questions in the front of the form and you start adding in the numbers into the correct boxes.
This is straightforward until you start to realise, perhaps you are not sure exactly which number to put where, you are not sure if you have received the correct additional tax return pages and you may not have the correct information from your bank, employer, agent etc.
When I am asked to review a tax return that has been completed by a client themselves I have always found problems and most of these would have meant too much tax was paid or too much information was given.
A key part of tax returns now if risk management. If you include too much, HMRC can dig around in other areas or if you include too little HMRC can declare your tax return was not sufficient. Any tax return that is completed with obvious mistakes and looks un-professional is going to attract attention. This attention means HMRC can ask in detail about all aspects.
One of the greatest reasons for using a qualified chartered tax adviser to prepare your tax return is certainty that these issues have been considered and your return arrives with HMRC as perfect as possible to minimise risk of enquiry by HMRC. Peace of mind for you.