How is Zakat on wealth calculated for someone who does not save money separately, and whose capital is in his freelance business which depends on his receivables and payables?

You must determine the first year you possessed the نصاب (85 grams of gold or 595 grams of silver) by asking owners of gold and silver shops. Zakat (definition) is calculated at 2.5% of the money you possess and what is owed to you by others, after deducting your own debts. For zakat to be obligatory on debts, they must be owed by a solvent person who is neither procrastinating nor denying the debt. Otherwise, zakat is not obligatory until the debt is collected, and then it is to be paid for one year, even if it remained for years.