One possible answer, suggested to the French press by sources close to Hallyday, is that he wants to live tax-free in Monaco. Hallyday, aka Jean-Philippe Smet, 62, confirmed 10 days ago that he had applied for Belgian citizenship, which would involve renouncing his French nationality.
In an interview with Paris-Match last week, he said his only motive was to rediscover his roots and exorcise the "demons" left by his Belgian father, who abandoned him as a child.
"This story, or rather the absence of any story, between my father and myself ... has disturbed me all my life. It still haunts me," Hallyday said.
Sources in his entourage, however, point out that a change of nationality could have a more tangible benefit.
Johnny Hallyday earned €6.6m (£4.5m) last year, the highest earnings of any French singer. He is estimated to have paid more than €4m in taxes to the French government. He insists he has no intention of following other wealthy French people into Belgian tax exile. But the sources told the newspaper Libération that in the future he could set up home in Monaco.
Under the tax treaty between France and the tiny principality on the Mediterranean, French residents still have to pay taxes in France. Other nationalities, including Belgians, pay no income tax.
But Hallyday told Paris-Match: "I will continue to live in France. My [adopted 17-month-old Vietnamese] daughter will go to school in France. I will pay my taxes in France."
The star starts a new French tour in April and is planning his first venture into the blues.Reuse content