Hi @lynnmath ,

You're required to start paying GST from the time your earning went over the $30000 threshold. CRA does allow you to set the effective date by 30 days. I'd recommend you take the following steps 

1. Register for a GST number right away

2. Call the CRA to confirm your GST payments, you might need to provide proof (through invoices) if it has been more than 30 days since the transaction that took you over the $30000 threshold.

You can refer to the following pages:

https://turbotax.intuit.ca/tips/self-empl[product key removed]cting-gst-hst-8730?srsltid=AfmBOopDMhj...

https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/gst-hst-businesses/when-regis...