Is there a limit on the period IR can go back to investigate a tax return? Is this the same for personal and business (Ltd co) returns? I run a very small business and I have just started using an accountant to sort out my accounts, which I used to do myself. Turns out I made a mistake on the 2003/2004 company return (in my favour naturally) of about �200. Should I keep quiet about it, or tell them. What are the chances of this ever coming up?