You should almost always file a tax return, even if you have no income.

First and most importantly: the CRA uses the information from your return to determine your eligibility for benefits, including the Canada child benefit and the Canada groceries and essentials benefit. If you have a spouse or common-law partner, they need to file too so the CRA has both of your incomes. Filing on time ensures that you'll continue to get these benefits.

Second, while you might not need to file a return if you don't owe tax, it's also the only way to request a tax refund. In some provinces you might get a small refund just for filing your taxes, even if you didn't pay any tax this year.

Finally, it's very easy to file a tax return when you have no income to report (and it's good practice for when you do)!