Dr. Monzer Kahf, a prominent economist and counselor and he gave the following answer: “Zakah is on net assets, with the exclusion of those used for residence. If the machines are not that expensive and the business owner can hardly make it for paying the bills, most likely there is no due Zakah on this kind of business. Anyway, one should evaluate the machines for current prices and any inventory if any, add cash on hand and in bank and add accounts receivable if any, then deduct from the total any loans and debts on the business or the owner’s person, if the final residual is equal to US$ 1000 or more (this is approximately the amount of Nisab) and that much is still with the owner after a lunar year from the date a Nisab existed for the first time, then Zakah is due at the rate of 2.5% every lunar year from then on (a lunar year is 354 days).”