All perfect praise be to Allah. Blessings and peace be upon Prophet Mohammad.
If the collecting agent collected the sums due for the doctor and gave them to him, and took an agreed upon fee- a specified sum, or an indefinite percentage- then it is permissible because it is a form of proxy for a wage.
Nevertheless, it is impermissible for the collecting agent to pay the doctor`s due sums from his own pocket after deducting his wages, then recollect them from the party in question because such an act involves Ribaa (usury). This is similar to “ discount of bank bills” which is-in Sharia- a loan given from the bank to the client with the value of a bank bill, and after deducting the bank`s commission, in return for collecting the value of the bank bill on its due time later on.
This transaction involves Ribaa An-Nasee'ah ( an increase in the amount due, in return for a delay in payment) and Ribaa Al-Fadhl ( exchanging goods of the same kind with an increase in quantity e.g. one kg. of rice for two kgs.) because the agent had bought a certain sum to the doctor for a lesser delayed sum. The Prophet (PBUH) said: “There is no Riba (in money exchange) except when it is not done from hand to hand (i.e. when there is delay in payment.” {Muslim}.
In its seventh session, the International Islamic Fiqh Academy forbade the discount of bank bills.
Therefore, deducting the collecting wages from the sums that are pre-paid to doctors, then reclaiming them from insurance companies is impermissible in Islamic Law. Resolution ( No.73) by the Jordanian Board of Iftaa` adopts the same opinion. And Allah knows best.