Bad news for those completing a paper tax return. The deadlines have changed. Last year, you had to get it in by January 31 to avoid a fine. This year it's October 31 - three months earlier. If you don't manage it by that time, you will be fined £100.
That's because, for the first time, the dates for filing online returns and paper returns are separate. The tax office really wants you to file online, which is why you have until January 31 to do so. But, if you are still intent on sticking with paper returns, then it's October 31. After that date, you could avoid the fine by filing online. As for who needs to fill in a return, the answer is simple.
If they send you one, you need to fill it in. But if they don't send you one and you have quite complicate tax affairs, such as lots of savings income or capital-gains issues, you should call the tax office and let them know about it. It's up to you to let them know.