IDOC "ACC_GL_POSTING01" fails du to missing OBJ_TYPE

Dear experts,

I need to post to a Leading Ledger (OL) account using an inbound iDoc.

I found I could use iDoc ACC_GL_POSTING.ACC_GL_POSTING01 iDoc to do that.

The BAPI "BAPI_ACC_DOCUMENT_POST" is used by that in the background if I am not mistaken.

In WE20 I set message type "ACC_GL_POSTING" and Process code "BAPI" and "Trigger immediately".

The iDoc is filled as follows:

E1BPACHE08

OBJ_TYPE

OBJ_KEY 20150701

OBJ_SYS <target client>

USERNAME <user>

HEADER_TXT

OBJ_KEY_R

COMP_CODE 0104

AC_DOC_NO

FISC_YEAR

DOC_DATE 20150701

PSTNG_DATE 20150701

TRANS_DATE 20150701

FIS_PERIOD

DOC_TYPE SA

REF_DOC_NO 0000000000006066

COMPO_ACC

REASON_REV

REF_DOC_NO_LONG

ACC_PRINCIPLE IAS

But whenever I post the inbound iDoc ACC_GL_POSTING01 I get the error:

"Required field OBJ_TYP was not transferred in parameter DOCUMENTHEADER

Error in document: 20150701 ET2CLNT100

Message no. RW609"

I know I need to fill iDoc field OBJ_TYPE but with what value? I checked table TTYP for values but I do not know which value to pick from there.

Please help. Can you suggest how to find the right value from TTYP? It seems the only obstacle righ now.

Thank you and best regards,

Peter