If your income tax refund has been issued to you by cheque in previous years, it will never expire.
Any uncashed cheques from the CRA never expire or become “stale-dated.” If your cheque was stolen or destroyed, you could request a duplicate payment by contracting the CRA or signing into your My Account portal and select “Uncashed Cheques.”
Suppose you find an uncashed cheque and your financial institution is unwilling to cash it. In that case, you can mail the cheque to the Imaging and Receiver General Operations Directorate and ask to have the payment reissued.