How can I check how much I spent by category?

Hello there. Let me help you check how much you spent by category. 

You'll want to run a profit and loss report to check on your expenses. Let's make sure to filter out your desired details. 

Here's how: 

1. Go to Reports, and search Profit and Loss.
2. On the page, click Customize. 
3. Press the dropdown Filter and select All Expense Accounts. 
4. Once done, Run report.

Additionally, I've added this article that allows you to save the current personalization settings of your report: Memorize reports in QuickBooks Online.

Feel free to reply to this thread for any additional assistance in running your reports in QuickBooks Online. I'll be here to assist.