Jonkinloch24

Hello, I run a small business that has recently seen some growth. To help with that growth, I am taking on a co-founder by vesting them equity over 5 years. I know the new co-founder must pay income tax on the equity (and also capital gains tax when the time comes) but my question is this: If the new co-founder is vesting equity over 5 years (or longer) then do they pay the tax each month on what has been vested only? For example, if its a 5 year vesting period at £50,000 income tax, then do they pay £833.33 each month as the equity is vested at 1/60? Or would they be required to pay the full £50,000 at the start of the vesting period? Thank you in advance