Conversation so far:
When did Ernie Kovacs exihibt tax evasion?
A frequent critic of the U.S. tax system, Kovacs owed the Internal Revenue Service several hundred thousand dollars in back taxes.
What happened that caused Ernie Kovacs to owe back taxes?
Kovacs owed the Internal Revenue Service several hundred thousand dollars in back taxes, due to his simple refusal to pay the bulk of them.

Question: how much did he evade?
Self-contained rewrite: how much did Ernie Kovacs evade in taxes?