We have a monthly donor that we haven't been able to contact for 2 years. They are direct debit, so we don't need to update card numbers. Last year for their annual tax receipt, it came back as invalid mailing address. Tried to call, phone number not in service and their email is no longer valid. With not having any contact, ethically I feel we should cancel their donation as we cannot even issue them a tax receipt without a valid address. Nothing on the CRA I can find says anything to the matter. Would love to hear thoughts and opinions on next steps.