Tax code & does not appear in any G/L account item

What causes this issue?

The document entered contains a customer or vendor item with tax code
&V1&. This does not occur in any of the G/L account or material items.
Note that such postings are incorrect, meaning that there are tax
notification items for which there are no tax-relevant items in the
accounting document. The tax notification items are derived from the
accounting document.
Consequences:
If you have not entered the cash discount base manually, the system will
set it to zero in this item.
If this item was paid with cash discount deduction and the cash discount
amount contains a tax portion, the tax code entered is used for the
backdated tax calculation. An automatic breakdown does not take place on
the basis of the offsetting items.
Tax notification items that cannot be explained by the accounting
document appear in reporting.

How to fix this error?

Check whether the tax code was set correctly. If necessary, correct it
or enter "**".
There are, however, also situations in which it makes sense to enter a
tax code that differs from the offsetting items manually, for example,
during data acquisition. If you deactivate the error message, you allow
this type of inconsistent postings. SAP is not accountable for this. The
posting items of an accounting document should always be able to explain
the tax notification items of the accounting document, which is not the
case if this error message is raised.
INCLUDE 'CUSTOMIZED_MESSAGE_INFO' OBJECT DOKU ID TX

Error message extract from SAP system. Copyright SAP SE.