The basic rule for filing your Canadian corporate tax return is that you must file your return no later than six months after the end of each tax year.
So when your T2 tax return is due depends on your corporation's fiscal year end. If, for instance, your corporation has a fiscal year end of June 30th, your Canadian corporate tax return would be due on December 31st (the last day of the sixth month).
If your corporation's fiscal year end falls on a date during the month rather than at the end of the month, then your T2 tax return Canada be filed by the same day of the sixth month after the end of the tax year.
If, for instance, in the example above, your corporation's fiscal year end was June 16th rather than June 30th, your Canadian corporate tax return would be due on December 16th of that year.
And if the filing deadline for your Canadian corporate tax return is a Saturday, Sunday, or public holiday? The Canada Revenue Agency advises that "we will consider the return filed on time if you deliver, mail, or transmit it on the first business day after the filing deadline."
Note that you must file a Canadian corporate tax return every year, even if your corporation did not make any money – and it's important to file your T2 tax return Canada on time, or you will incur late payment penalties.
If you have any doubts about your situation, don’t guess; contact a tax professional or local tax office and explain your situation.