You can file income tax return for last two assessment years in this current financial year. So, in this AY 2017-18, you can file income taxes for previous financial year 20116-17 and last two financial years which are AY 2014-15 and AY 2015-16. If you want to file ITR for other than these years then it is not possible.Tax filing beyond last two years is only possible when you receive any such notice from the income tax department.You can also contact Assessing Officer (AO) in the nearest income tax office and file a manual return for the financial years older than 2 years.you can easily understand file ITR by this video:-If you require more guidelines on filing ITR for previous year, you can subscribe to expert services to get personal consultation over this issue. You can find cheaper services for the same with www.allindiaitr.com.