idoc load aborting with partner not found error

[BradMiller]

I am trying to create an sample idoc in SAP sandbox.I created a control record and a mandatory cremas01 segment in the transformer stage and loading that data into SAP using idoc load stage but it aborts with the following messages.

1)"Fatal Error: Fatal: IDOC_F_00118`:`Required property 'PARTNER NUMBER' not found." - I cross checked the partner no in SAP which I passed in transformer and its correct & matches the SAP partner no.

2) Error in writeBlock - could not write 16

Could you please suggest me what could be the cause of the problem.