Chinese authorities are closing down the firm handling Ai Weiwei's affairs, the outspoken artist said on Monday, possibly saving him from paying the remainder of a 15m yuan (£1.5m) tax fine.

The 55-year-old said he believed he and his team had lost the battle but won the war, after a court rejected his appeal against the charges last week.

Officials said this weekend they were removing Fake Cultural Development's business licence because it had not met annual registration requirements. The company has been unable to do so because police confiscated all its materials and its stamp when they detained Ai last year.

"I think it could be an excuse not to give us a fine," the artist added. Ai's lawyer, Liu Xiaoyuan, said it was not clear how Fake could pay the 6.6m yuan outstanding if it had no licence. But he added that he had filed a request for a hearing into its closure.

Ai's supporters have always said the fine and his 81-day detention were in retaliation for his social and political activism, while Chinese authorities insist the case was unrelated to human rights and was solely about tax evasion. He was held amid a broader crackdown on dozens of activists, lawyers and dissidents.

Thousands of supporters sent Ai money to help pay an 8.45m yuan bond, allowing him to challenge the charges. After his appeal was rejected he said he would refuse to pay the rest because he did not recognise the fine, adding that he suspected authorities would be too embarrassed to collect it.

"I think they want to back down to try and conclude this case. From the beginning they should not have had it; they were using very old tactics to punish someone and make up a crime to make people think 'He's a bad guy' … That didn't work and it backfired. I think it completely failed," he said on Monday.

"Of course they didn't like the fact it had gone on so long and could last longer."

Ai added that he had mixed feelings about the long-running case.

"Of course we have lost the battle – they kept our [tax deposit]. But I think we have won the war. We gave people a clear understanding of what the Fake case was about and how they handled it," he said.

He said he hoped it would mean that they could not do the same to anyone else.

"No great nation should play dirty tricks on its citizens," he said.

Chinese authorities could not be contacted as Monday is a public holiday in China. They have made little public comment on his case in the past.

Nicholas Bequelin, senior Asia researcher at Human Rights Watch, said: "The tax case against Ai Weiwei was politically motivated from the outset – an 11th-hour pretext pulled out of a hat by the government to justify Ai's unlawful arrest and secret detention for 81 days.

"The authorities are dealing with Ai in the time-honoured tradition of making critics 'wear small shoes' as the Chinese expression has it: a never-ending series of petty bureaucratic harassment and administrative vexations designed to wear down its victim.

"While Ai may have scored a moral victory in the tax case, the government has yet to restore his freedom to travel, return his passport, lift the tight police monitoring he is the target of, and allow him to resume the civic initiatives that first landed him in trouble, from filming interviews of social activists to pressing for accountability in the collapse of schools during the 2008 Sichuan earthquake."

• Additional research by Cecily Huang