Final answer:
The tax return for Corporation XYZ, Inc. with a tax year ending on August 31st would be due on September 15th, but if they filed an extension, the deadline would be December 15th.
Step-by-step explanation:
The tax return for Corporation XYZ, Inc. would be due on September 15th if they have a tax year which ends on August 31st. This is because for corporations with a tax year ending on a date other than December 31st, the tax return is due on the 15th day of the ninth month after the end of their tax year.
If Corporation XYZ, Inc. filed an extension, their tax return would be due on December 15th. Filing an extension grants corporations an additional three months to file their tax return, but the deadline is still the 15th day of the ninth month.