[LatteLazy]

That’s tax evasion.

Money laundering is disguising the source or use of funds (making illegally sourced cash look legally sourced).

Plenty of people would (do) happily pay some tax on cash as part of avoiding difficult questions about the source.

[bluGill]

They are often related though as if you have illegal money you also didn't pap taxes on it and in turn they can get you because they may not know where the money is from they know you spent more than your taxes indicate is possible.

[XorNot]

Related but entirely different purposes. Paying taxes on illegally sourced money is basically the goal, because it makes it legal - it gives you a declared income and means future transactions look within your means.

Tax evasion conversely makes legally earned money somewhat illegal to the evader (though generally fine for anyone else to handle accidentally).

[bluGill]

Paying taxes doesn't make illegal things legal. However it hides evidence. Al Capon was got on tax evasion because exidence of that was easier to prove. Everyone knew is other crimes - but there wasn't enough evidence to convict.