I mean, it depends if the amount is $10billion or $10, but generally they start by sending you a letter at wherever they think you live saying "hello, please wr

I mean, it depends if the amount is $10billion or $10, but generally they start by sending you a letter at wherever they think you live saying "hello, please write us a check for $x, thanks". Then they do that... again. At some point they probably put your name on some kind of list of Bad Taxpayers but unless we're talking millions here they probably aren't sending agents after you in specific.