If an individual's fiscal year ends on June 30th, when is his tax return's due date?

Individuals no longer can file tax returns on a fiscal year basis.

In the unlikely event that there is still one from decades ago that started out on a fiscal year basis and remains there (they would be VERY old, in 46 years of tax practice I've never met one) the filing deadline is the 15th day of the 4th month following the end of the fiscal year. That would be Oct 15 for a fiscal year that ends on June 30.

Actually it is legal for an individual to file a fiscal year, BUT they'd have to either do it with their first return *or* get permission from the IRS to switch to it. The odds of an indivdual meeting the test for "maintaining their records on a fiscal basis" are very low.

The only fiscal year return I've encountered for an individual was an adult from the UK who was dual status (their filing year is different) and she originally thought it would be easier to match the UK. I was helping her fill out the forms and short year return to switch to calendar.

an individual doesn't have a fiscal year, only businesses do