Will my existing IELTS score be accepted for master's programs in Ireland and Canada, given that it meets each university's requirements?

Your score being high enough is only part of the picture. What actually decides whether it is accepted is whether it meets the specific program's band requirements and whether it is still valid on the date each university or immigration authority checks it.

What to Verify for Each Application

How Ireland and Canada Differ Slightly

In Ireland, universities set their own course requirements, but Irish immigration separately requires your English certificate to have been issued within 2 years of your expected course start date, so even a university accepted score can fail the visa stage if it has expired by then. In Canada, universities like Simon Fraser and Waterloo similarly require your score to be valid at the time you submit your application, generally within 2 years, with no separate federal IELTS rule beyond what each institution sets.

My Advice

Check your test date against both the university's application deadline and your intended course start date, not just today's date, since a score that looks valid now could expire before you actually begin your course. If your IELTS is close to the 2 year mark and you are applying to multiple programs across both countries, consider retaking it early rather than risking a rejection over an expired certificate.