However the guide is ambiguous as to whether it refers to line item Tax Details or document Tax Details (seems to be the former). It tells you to join additional tables on Line Item Sequence, but leave the Tax Detail ID unlinked (when linking to the Sales Taxes Work and History Table, SOP10105). This leads to unexpected behaviour as we want the summary Tax Detail of the document, not that of individual line items.
On an Irish invoice with line items with GB tax details, I was only seeing the GB VAT Number and Rate on my client's reports.
The method that worked for me was to remove the link on Line Item Sequence between the tables described in the first KB article. Then to add a restriction to the report definition specifying that the Line Item Sequence on Sales Taxes Work and History should be 0.
Finally this gave me what I wanted: The Irish Tax Details on a document containing items set up with GB Tax Details where previously I could only see the GB details. Repeat for the other SOP Blank Documents.
Obviously, to get separate Tax Details for individual line items, the guide should work, but it doesn't when the document tax is not based on the line items but the customer record.