What is the effect of garden leave?
Bonus terms normally specify what will happen if an employer puts an individual on garden leave after notice is given (by either party). Most frequently, the bonus will no longer be payable but redundancy may sometimes be a carve-out from this provision. If the contract is silent, and the bonus is a payment for previous achievements (e.g. sales performance over the past year), and not an incentive for the coming year or a reward for loyalty then it could be payable (at a rational level) despite the individual being on garden leave.
If a bonus is stated to be conditional upon someone’s “active employment” this will ordinarily mean that they are not entitled to it even if they are on garden leave.