Belgian tennis star Kim Clijsters is considering an offer to take on Australian citizenship for tax purposes, her father and manager Lei said.

"Australia's tax authorities recently asked me to talk about an advantageous fiscal arrangement," Lei Clijsters told the daily De Morgen. "Of course, linked to the possible advantages is naturalisation as Australian citizen."

Kim Clijsters, 19, is the girlfriend of world No.1 Lleyton Hewitt and already spends a lot of time in Australia. Lei Clijsters said she is considering the switch because of Belgium's tax system, which has some of the highest rates in Europe.

"In the past five years, we have paid an incredible amount of taxes," Lei Clijsters said, adding tax authorities keep up to 60 percent of earnings won by the world's No.4. "Little wonder we are open to offers which cost us less."

Clijsters has won in excess of $US3 million ($A5.38 million) in prize money since turning pro in 1998.

She has had a stellar year, reaching the Australian Open semi-finals and beating the Williams sisters on her way to the Masters title last month. She also won tournaments in Hamburg, Filderstadt and Luxembourg and briefly rose to No.3 in the WTA rankings.

Lei Clijsters said that despite considering Australia's offer, Kim was still firmly attached to her Belgian roots.

"She always said she wanted to remain Belgian, but as her manager I have to study all offers and we cannot reject this without examining it carefully," he told Le Soir newspaper.

Lei Clijsters complained that soccer players in Belgium get more financial protection than other athletes and called on tax authorities to offer her daughter a better financial deal.

Several Belgian sports stars have left Belgium for tax havens such as Monaco for tax purposes but few have actually switched citizenship.

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