How to add class in trial balance ?

Welcome to the Community space, almalki. 

I understand you want to generate and filter the trial balance report by class. Currently, the trial balance report is unable to filter class. However, you can run the General Ledger or Transaction Detail by Account report to filter transactions by class.

1. Hover to the Reports, then enter General Ledger in the search bar.
2. Click Switch to classic view, then tap Customize.
3. Click Change columns and tick Class. 
4. Click Filter, then tap the Class dropdown and select a specific customer if necessary. 
5. Once done, hit Run report. 

By exporting and consolidating both Trial Balance and General Ledger reports manually add a class column and enter more necessary details.

Furthermore, I'm adding this helpful article as your guide in sending reports in QBO: Set schedule and email information for a memorised report.

Return to this post if you have other concerns about customizing reports in QBO. I'll be around to lend a hand.