How to you have a sum amount in custom report

I can help you customize a report showing the total amount, barcode1. 

Before anything else, I'd like to ask what report we are currently running so I can provide the detailed steps on how to customise it. If we've pulled up a transactions list report, we're unable to sum up the amount. However, we can export it to Excel and add them in there. To do that, just click the export icon at the upper-right of the report. Then, select Export to Excel. 

If we're running a report let's say the Sales by Customer Detail, the transactions are subdivided by customer and has a total amount as well. I'll surely send a feedback to our engineers to also have a way to add a Total row for every report we'll run. If you need more help with cutomising a report, just click this article: Customise reports in QuickBooks Online. 

I'll be here if you need any help. Take care and keep safe!