The concrete agreement is the first point to examine.
Set out the wording or matching statements about the work, the later benefit and any remuneration. Section 1152 of the Austrian Civil Code presumes reasonable remuneration where no remuneration was fixed and unpaid performance was not agreed.
The key issue remains whether the work was actually based on that agreement. Letters, messages, transfer agreements, witness evidence and business records may show the connection between the performance and the expected benefit.