Is it obligatory to pay Zakat on wealth on the date it reaches the nisab, or is it permissible to pay it in Ramadan, and what are the consequences of delaying it if it is not permissible to pay it in Ramadan?

If you do not know when the wealth reached the nisab (minimum threshold for zakat), then you must strive and investigate to determine the time of obligation. If you are not certain, it is sufficient to act upon the preponderant opinion, as Allah Almighty says: "Allah does not burden a soul beyond its capacity," and "Ruling based on the preponderant opinion is a fundamental principle in legal judgments." If the wealth is cash, you can refer to the bank statement to determine when the wealth reached the nisab. It is permissible to pay zakat in Ramadan as an advance payment before the time of obligation, according to the majority of scholars, including Imams Abu Hanifa, Al-Shafi'i, and Ahmad, provided that one possesses the nisab.