Hi sherrilrflint,
Thanks for reaching out! Choosing the proper settings in your report is important to produce accurate information for your business needs. QuickBooks Online gives you the flexibility to easily switch between the cash and accrual basis. I'll be happy to show you how.
When running your GST report in QuickBooks Online, you'll see an Accounting method section (usually beside the Run Report button). This section allows you to select between Cash and Accrual before running your report. If you're unable to switch between them, it could be due to a browser issue. Temporary internet files that accumulate in your browser can sometimes cause bugs in the software. To ensure your app or browser is running the program as designed, I recommend following the troubleshooting steps in this article: Clear cache and cookies to fix issues when using QuickBooks Online
In case you need assistance on how to run reports in QuickBooks Online, here's an article: Run reports in QuickBooks Online
I hope this helps! Feel free to stop by any time if you have more questions.