Will Resigning After My Work Anniversary Affect My Retention Bonus Eligibility?

I have a yearly retention bonus clause in my employment contract. I complete my one year on 26/04/2022. However, it's going to be paid in the month of May due to the attendance cycle being from the 21st of this month to the 20th of next month.

If I resign on 27th April and serve my 30 days' notice period, will I still be eligible for this bonus?

This is a voluntary payment by your company, and it would depend on the rules in this regard as to whether you will be paid a retention bonus or not. However, the general rule is that a resigned employee is not paid such incentives.