Main partner not defined for billing type S1

Hello guys,

Please, I am trying to cancel a billing document through transaction VF11 but I am getting the following error:

Main partner not defined for billing type S1

Message no. 8B516

Diagnosis

For Nota Fiscal relevant billing types, a mainpartner must be defined.

Procedure

Please define a partner.

Does anybody know what I can do?

Thank you,