When should Zakat be paid?
A: The four mainstream schools of Islamic jurisprudence, namely, the Hanafi, Shafi’i, Maliki and Hanbali schools are all in agreement that the payment of Zakat is due immediately upon one’s anniversary.
Zakat is an immediate obligation as Allah has instructed us to pay immediately in the following verse: “And give its due on the day of its harvest.” (Qur’an 6:141)
And Allah knows best!
see links: https://help.nzf.org.uk/en/article/when-is-zakat-paid-12jvgr1/
https://help.nzf.org.uk/en/article/is-there-any-special-virtue-for-paying-zakat-in-ramadhan-k5cymx/