SAP Note 21418 - MR01: Tax code cannot be entered

Symptom:

MRHR / MR01:
When posting an invoice for an account-assigned purchase order, no tax code is generated. Field 'Tax code' (BSEG-MWSKZ) is not displayed on screen 'Individual Order Item'.

Cause and prerequisites

This is caused by a missing setting in FI Customizing (Transaction: FS02 - Change G/L Account).
For the G/L account which comes after the account assignment of an order item, no entry exists in the account control for the tax category. As a result, this account is looked at as not tax-relevant and no tax code is generated which can lead to the above-mentioned reaction.

Solution
First, determine the G/L account which is stored in the purchase order for this item (Transaction ME23, Overview (F5) then dispplay the account assignment for the item).
After this, change the tax category (SKB1-MWSKZ) to '-' (Only input tax allowed) or '*' (All tax types allowed) on the second screen in the GL a/c master record using Transaction FS02.
If field 'Tax code' is not ready for input, change the field selection (Transaction OBD4) for this field to 'Optional entry'.

Additional key words

M8159