In the US (where the forum is based), both tax payments, and tax returns are due on April 15th of the following year for the prior year's tax period. If you are unable to complete your tax return by April 15th, then you can request an automatic 6 month extension (you still need to have 90% of your tax due paid by April 15th), which would move the due date to file to October 15th.

There are situations in which an additional extension could be granted, however theymos most likely does not qualify for any of these.