How can I run a specific report of my customers that haven’t purchased from us in the last 6 months?

Hello ben-peacock-mail

Thanks for posting in the Community! 

You can run the Transaction List by Customer or Sales by Customer Detail report in QuickBooks Online. These reports will show the date of the last invoice you have for a specific customer. Here's how:

1. Click on the Reports tab.
2. On the search box type in Transaction List by Customer or Sales by Customer Detail.
3. Select the report name, and click on Customise button.
4. Select a Report period and accounting method.
5. Click on Rows/columns or Filter to add a piece of specific information to the report.
6. Click on Run Report.

You can also save the customised report in your QuickBooks Onlne account to check on it later. Also, you can refer to this link to learn more about Customise reports in QuickBooks Online.

Post again in the Community if you have more questions about QuickBooks Online. I'll be around to help you!