Within the Postdoctoral Fellowships one of the obligations of the researcher is “not to receive, for activities carried out in the frame of the action, other incomes than those received from the beneficiary or other entities mentioned in Annex 1.” (p. 94 of the Horizon Europe Model Grant Agreement for Unit Grants).
Additional payment is authorised if it is provided by the beneficiary recruiting the fellow.
COFUND programmes are co-financed and additional funding on top of the EU contribution is to be included in the project proposal.