Invalid account assignment combination in document/item &2; see long text

What causes this issue?

The document could not be posted because it contains an invalid account
assignment combination.
The relevant data includes:
Validation strategy: &V1&
Verified line item: &V2&
Ledger group: &V3&

System Response

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

How to fix this error?

Check the account assignment combination in the document.
Where applicable, also check the validation rule used (&V1&). You do
this in Customizing for <LS>Financial Accounting Global Settings</>
under <DS:SIMG.FAGL_VALIDATE_DC> Define Validation Rule for Account
Assignment Combinations</>.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.