If you make a mistake on your tax return, you've normally got 12 months from 31st January after the end of the tax year to correct or amend it. For example, if you send your 2014/15 online tax return by 31st January 2016, you have until 31st January 2017 to amend it. You can only amend your return after this timeframe if you received your return late (after 31st July).
If you owe more tax or have to pay a penalty as a result of the mistake, HMRC should tell you how much you need to pay and when and how to pay it. If you think you're due a refund you can tell HMRC how you’d like to receive it.
If you sent your tax return electronically, you can also amend it online. If you send it in hard-copy, you don't need to send in the whole tax return again. Just write to HMRC and attached the pages you want to change.
If preparing your tax return is becoming a burden, please feel free to contact us. Your local TaxAssist Accountant would be happy to prepare your return for you. This should ensure your return is accurate and prepared in good time; and your TaxAssist Accountant will also look for any tax saving opportunities.