The combination [Item &, TaxCode &, JurCode &, JurLevel &] is not unique

What causes this issue?

You are posting a document for which the tax records cannot be uniquely
identified.

System Response

As a result the tax data may not be completely updated to the external
system.

How to fix this error?

Check the assignment of the alternate condition type formulas in the
tax procedure or, in case of SD, the customer pricing procedure.
The following is an example of a configuration that leads to this
message: For one tax code, such as O1, two different tax condition
types, for example, XR1 and XR2 are active for the same line item and
have the same alternate condition type formula, such as 301.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.