Welcome to the Reckon Community and thank you for your question.
Unfortunately you cannot add a separate column for tax amount on supplier unpaid bill detail report.
Workaround: I have created a bill for $110 with tax amount $10.00, then went to reports > custom transaction detail report > modify report > select display option & under columns tick tax amount which in turn display the split transaction with tax amount:
We hope the above helps you resolving your issue. If you need further assistance, please let us know.
CheersMustafa
"Working with Accountants/Bookkeepers PPs/APs, as an independent IT Professional and retired FCPA Accountant"