Is the method of calculating Zakat on medical clinic income correct, taking into account that the final calculations are made in the fifth month of the following year and the difficulty of accurately calculating expenses during the Hawl (Zakat year)?

Zakat (definition) is not obligatory on the clinic, its equipment, and its furnishings because they are not intended for trade. Zakat is only obligatory on the financial returns generated from it if these returns reach the nisab (definition) (minimum threshold) and a complete hawl (lunar year) passes over them. One must know the time when the wealth reached the nisab according to the Hijri calendar, and the Zakat should be disbursed at this time every year. A specific day can be set for this, even if it means expediting the Zakat payment. It is not permissible to delay the disbursement of Zakat beyond its due time. If the time becomes due and you are unable to estimate the exact amount, you should make your best effort to estimate and disburse what you are certain is obligatory, then disburse the remaining amount if any, after completing the calculations. If you disburse an amount that you are certain is in excess and you intend it as charity, that is sufficient for you. As for the wealth gained during the hawl, it is not obligatory to combine it with the principal wealth for the hawl if it did not result from the growth of the principal; however, if it is combined, that is good. The deduction of debts is a matter of scholarly disagreement.