The Tax Office is targeting people who've missed a tax return -- even if it was a decade ago when they were in school. Here's what the ATO is up to and how to avoid a hefty fine if you've done nothing wrong.

Have you failed to send in a tax return for any year since 2000? If the answer is yes -- even if you were at school at the time -- watch out. The Tax Office may send you a letter threatening to fine you thousands of dollars or throw you in prison if you don't file it right away. But don't panic. While the letter is not a scam, the Tax Office is trying it on in some cases and appears to have misrepresented the penalties. Crikey understands the ATO has new targets to reach on non-lodgement of returns. So read on to beat the taxman's fishing trip for revenue. In response to a tip , Crikey has heard from people all around the country who have received the letter. Some are upset or stressed. The letter says you've missed a tax return, names the years, and threatens you with a fine of up to $4250 -- charged at interest of 9.59% per day -- if you don't "lodge immediately". If convicted for failure to lodge, you could be "imprisoned for up to 12 months". While plenty of people who've got the letter probably did the wrong thing, may owe the ATO money and are ripping off society, some are being unfairly targeted. Some were aged 14-18 for the year in question and earned little or no income. Others were overseas. Some were never supposed to file a tax return. The ATO is targeting lawyers and people with a role in the taxation system. Here's the letter sent to a reader, H. He missed tax returns for 2003, 2004 and 2005 -- when he was in years 10 to 12, and earned no or little income. H rang the ATO and was told he must perform a "self-assessment". "I wonder whether their time would be better spent chasing real tax evaders and cheats, rather than high school students," H told Crikey.