Slap-happy Katt Williams better learn to take it like he gives it -- because the IRS just walloped the comedian with an astronomical tax lien ... totaling over $4 MILLION.
Uncle Sam filed the lien against Williams, claiming the comedian failed to pay $3.2 million in taxes in 2008 ... and also bailed on another $829,352 in 2009.
Source: TMZ. Read full article. (link)