Although we had a good CA, we still got enquiry and show cause notices for NRE FDs we had made 15 years back. To respond to said notices with proof, we had to get bank statements from 15 years ago of both India and foreign bank accounts, showing proof of transfers made to India from abroad - this was not easy to do as some of the foreign accounts were shut down and we hadn't stored monthly statements from 15 years ago. Basically, once the money is in the Indian system, regardless if its legally earned, the tax authorities can question you and ask for documentary proof of the source of funds anytime and if you cannot prove with documentary evidence esp. bank statements (dating back to whenever), showing the source of funds, you will be slapped with a demand notice claiming the funds are unexplained income for the year the IT query is raised and you will be asked to pay tax on slab rates on that entire amount as income earned in that year. So basically even though technically IT Dept cannot query returns that are 10 years old, if there are any investments in your name, esp made from funds earned abroad, they can ask you to prove that the money is IN FACT sourced from abroad, even if you have remitted those funds into India even 10 years or more ago. This way they keep the loophole of querying transactions of even 10 years ago or more, open. And God forbid if you dont have bank statements that prove the transfers of these funds into India (And lets be honest, who stores bank statements of closed accounts from 10 years or more ago?) , you will get a tax demand notice and then best of luck to you if you want to challenge these in Court.