What is the meaning of invalid contracts, and does working as a waiter in a café that sells alcohol in non-Muslim countries fall under them, and what is the ruling on delaying Zakat while unaware of its obligation and the passing of the year?

Al-Qurtubi defined contracts as what a person binds himself to, such as buying, selling, leasing, marriage, or divorce. Contracts that conform to Sharia are valid, while those that violate it are invalid. The majority of scholars do not differentiate between invalid (fasid) and void (batil), whereas the Hanafis do. A person leasing himself for a forbidden act, such as distributing alcohol, is impermissible and void.