Is it permissible for a partnership to exist between a doctor and an investor, whereby the investor provides the funding, and the doctor provides his certificate, knowledge, and work, and the doctor receives a fixed annual sum for his certificate, in addition to 80% of the examination and imaging fees, while the investor receives the profits from selling medicines and 20% of the examination and imaging fees? And is the fixed sum for the certificate considered lawful?

The aforementioned formula is not valid. However, it can be corrected by making the premises and equipment the property of the investor, while the questioner contributes his experience and labor. The contract would then be an ijara (leasing/hiring contract). The majority of scholars stipulate that the ujra (rent/wage) must be a known, fixed amount and cannot be a percentage. There is, however, a narration from Imam Ahmad that permits a percentage. It is not permissible to combine a percentage with a known amount. It is preferable that the ujra be either a fixed salary only or a percentage only, to avoid the problem of combining the two.