Hi @knicky,
taxes do not need to be raised/increased. They need to be paid!
If you accumulate all not paid taxes from these big multi-national companies there would be more than enough money to finance a UBI.
And yes: some of them will raise their prices so we will pay for it at the end.
But what about "free" services like Google, Facebook, etc? They can't do that and simply make a little bit less money which will only "hurt" some investors at the stock exchanges.
These companies are making really big money without paying (almost) no taxes.
Think also about Amazon - making billions - disturbing the market with "impossible" low prices and not paying the minimum salary to their e.g. warehouse workers. This is modern slavery and the taxes are not paid.