Postings to vendor accounts are not supported in TRM, only postings to G/L and customer accounts are supported.
If you need a posting to a vendor account for some reason, you can use the BAdI TPM_ACCIF_TRAC (method ACCIT_EXIT) and replace some fields to create a vendor posting. Let us assume you post to customer in the moment, then you have to replace the following fields:
– KUNNR (set it to blank)
In standard postings to vendor accounts are not possible. The use of the BAdI is only a workaround to change the standard posting logic.
You will not find the field vendor in any reporting, not in the posting log nor in TPM20.
Please also note that the BAdI can be used if you do NOT create payment request, if you create payment requests than you may have to post to customer
or G/L account.
There are no plans to provide the vendor field in SAP standard.