TTM Trailing Twelve Months

I can see this is useful in your everyday task, @GrowUp. I can share a workaround so you can pull up trailing twelve-month reports in QuickBooks Online.

We export the report to an Exel file, and you can modify the file from there. Doing this will allow you to edit all the data in the Excel file. 

Here's how:

1. Go to Business Overview and select Reports.
2. Search for and select the report you want to export.
3. At the top of the report file, select the Export icon. Then choose Export to Excel.
4. Save the file somewhere you can easily find, like your Downloads folder.

Moreover, if you're experiencing missing data when opening a report in Excel, it's likely because the file is in protected view. To view the full report, you'll need to select Enable Editing in Excel. 

Alternatively, you can switch between the two views anytime without affecting your accounts or data. It allows you to choose the view that best suits your needs. See this reference: Switch between Business and Accountant view in QuickBooks Online.

Moreover, your feedback is valuable to us. We recommend sending your suggestion to our product developer and discussing this feature with them. Refer to this link for your guide: How to submit your feedback?

I'm here to help you with any questions or concerns under the Reports section. Feel free to ask me anything, and I'll do my best to provide you with a helpful response.

@GrowUp 

Obviously, @ChristineJoieR 's response doesn't help you.

TTM is not an available reporting period in QBO without manually changing the dates each time you run a report.  I can't tell you how many times having TTM (through the previous month's end) as an option would have been extremely helpful.    

I know this is a couple years old - but your in Quickbooks desktop you do a Reports>Custom Reports>Summary and make the columns by month and change the dates to the fiscal year and then you got it - trailing monthly!!