Hi,
Define Radio button in selection screen like,
CONSTANTS: C_X TYPE CHAR1 VALUE 'X'.
SELECTION-SCREEN : BEGIN OF BLOCK B1 WITH FRAME TITLE TEXT-001.
PARAMETERS : RAD1 RADIOBUTTON GROUP RAD1 DEFAULT 'X',
RAD2 RADIOBUTTON GROUP RAD1,
RAD3 RADIOBUTTON GROUP RAD1,
RAD4 RADIOBUTTON GROUP RAD1.
SELECTION-SCREEN : END OF BLOCK B1.
START-OF-SELECTION.
* Check RAD4 is checked.
IF RAD4 = C_X.
CALL TRANSACTION 'ZVAR_POS_TAX' .
ENDIF.
If you problem solved then mark as helpful or Correct answer.
Regards,
Hitesh