It's more complex than that. Poor people spend very differently than rich people. So assuming you just taxed everybody who was 'rich' (define any way you want)

It's more complex than that. Poor people spend very differently than rich people. So assuming you just taxed everybody who was 'rich' (define any way you want) to a level where you could fund UBI, then there would be no new money being introduced in the system. However what that money gets used for will change drastically. The 'rich' people would have used that extra money to either buy luxury goods or for saving/investing, the 'poor' people will mostly use that money to pay for food and housing. This change of can have effects on prices even without increasing the money supply.