Doing a 2019 tax return with an overpayment of CPP it is over 4 years I've override it and now I can't file it through Netfile?

As per the Canada Revenue Agency (CRA) :
Under the Canada Pension Plan, you must ask for a refund of your CPP over-contributions no later than four years from the end of the year the overpayment occurred in. 

For your issues, please contact the CRA directly at 1-800-959-8281.

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