What numbers do I use from the previous year's GST34 to complete the question about the GST370 Rebate? My services are zero rated, so I receive an HST ITC rebate.

Any rebate you received on your CCA, should be used to reduce your current CCA claim.

Any rebate you received on other expenses, you claim as income on line 10400:

• Search for GST370 rebate claim from the search engine on the top bar. 
• On the "2019 GST370 Rebate Claimed" page, enter the amount you received in 2020.
• You should be able to check this amount on line 10400 under your detailed summary

I hope this was helpful