Chinese artist and government critic Ai Weiwei is being pursued for nearly 2 million dollars (£1.24 million) in unpaid taxes and fines.
Mr Ai is barred from speaking publicly after being released on bail last week from nearly three months in prison.
But his friend Liu Xiaoyuan said Beijing's tax office had issued a notice to Mr Ai that he owed the money.
Mr Liu said he had seen the notice and that Mr Ai had three days to respond to it in writing if he objects.
Mr is the most high-profile target of a sweeping crackdown on activists this year.Reuse content