Restrict Withholding Tax change in not cleared documents

Question

Hello,
We want to adjust the Document chnage rules - OB32 in a manner that it restricts Withholding Tax fields from changing when the document is not cleared.
We tested & found that the Withholding tax fields as below when defined in document change rules are giving strange results.
BSEG-QBSHB          Withholding tax amnt
BSEG-QSFBT          Wthld.tax-exempt amt
BSEG-QSSHB          Withhold.tax base
BSEG-QSSKZ          Withholding tax code
BSEG-QSZNR          Exemption number
Of these the field BSEG-QSZNR - Exemption number field remains unmodifiable in FB02 when the document is cleared & also when it is not cleared. We tested it for Vendor & the settings were made for Account type K.
The field is always greyed out even if we make the field as modifiable in OB32.
The rest of the fields are remaining modifiable when the document is not cleared & become non modifiable when the document is cleared. This behaviour is not affected by whatever settings we make in OB32.
We tried to search for an SAP note for this peculiar behaviour but could not find one.
Could you please help.
Thanks & Regards
Shreenath

Answer 1

Dear Shreenath,
if You want to retrict, please delete from V_TBAER table the entries I suggested and then go to IMG > Extended Withholding Tax>Calculation>Withholding Tax Type> Define Withholding Tax Type for Invoice Posting or  Define Withholding Tax Type for Payment Posting -->
There will be a frame named  Control data; there please switch off the flag "W/tax base manual" and "Manual W/tax amount.
Please do a test and let me know.
Mauri