Please contact CRA at 1-866-864-5823 and inform them of your willingness to offset your refund with your debt. If you have a balance owing, the CRA may keep all or a portion of any future payments, tax refunds, or GST/HST credits until the amount is repaid.

Kindly see below additional information from Canada Revenue Agency (CRA)

Collection of overpayment 

If you require further assistance please contact our phone support team, or contact us directly on Facebook or Twitter.

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