MRQ error 13966 when trying to NetFile a TP1 or CO-17 return

Resolution

1. In ProFile, go to EFILE, then Options, then TP1 Internet and/or CO-17 Internet filing.
2. Choose Enter the NetFile QC Number and Access Code again.
3. Re-enter the NetFile QC number and access code.

If the error still persists, contact Revenu Québec to verify the status of the client's EFILE eligibility.