FRANKFURT, Germany (AP) _ When tennis star Steffi Graf left the Roman Catholic Church, it wasn't immediately clear if her quarrel was about religion or the tax collector.

Graf, whose previous tax troubles were international news, eventually insisted her decision was ``personal'' and not financial. Still, thousands of others have been leaving Germany's main religions in recent years to avoid paying a hefty church tax.

While the tax is not controversial, Graf's case illustrates how governments in Germany and other western European countries collect taxes, or funnel tax money, to religious organizations _ a system that would face strong opposition in countries with strict separation of church and state, like the United States.

Since the days of the Weimar Republic, registered church members in Germany have been billed the special tax by state governments to fund churches and their social services.

In Germany, the church tax amounts to 8 or 9 percent of an individual's income tax, and is normally withheld from the monthly paycheck.

Only members of minority religions in Germany, such as Islam, or unrecognized denominations, such as Jehovah's Witnesses or Scientology, are exempt.

To stop paying the tax, Graf had to file papers declaring that she had formally broken with the Catholic Church. The legal process is the same for a Lutheran or Jewish person opting out.

A German radio network reported that Graf may have owed the church up to $280,000 dollars in back taxes and quit when religious officials declined to reduce the amount.

But Graf denied that taxes played a role.

``My decision was based on personal reasons and shall please be respected as such,'' she said in a statement released by the WTA Tour last week.

Graf and her family have been dogged by other tax woes. Her father, Peter Graf, was convicted this year of evading $7.3 million in taxes on Steffi's earnings from 1989-93. He is now serving a prison term, and all of those taxes have been paid.

Germany's predominant Lutheran and Catholic churches acknowledge that the tax has contributed to declining membership in the 1990s.

During 1995, the most recent figures available, 168,000 Catholics and 296,000 Lutherans quit the churches.

The same year, the Catholic Church, with 27.5 million members, received some $4.7 billion from tax collections, and the Lutherans, with 28.2 million members, received $4.5 billion.

The trend of quitting churches over taxes soared after Germans had to start paying a 10 percent ``solidarity tax'' to finance the cost of the country's 1990 reunification.

``Apparently tax advisors told customers that the church tax and solidarity tax were about the same amounts and since one was voluntary it could be saved,'' said Heike Thome, a spokeswoman at the Roman Catholic Bishops Conference in Bonn.

With less church tax coming in, Thome said cuts in the social services Catholics provide _ including a vast network of hospitals, kindergartens, nursing homes _ are being considered.

Rosemarie Altenhofer, a Hesse state radio announcer in Frankfurt, said she dropped membership as a Catholic years ago, after a pastoral letter from the Vatican urged church members to vote for Germany's conservative Christian Democratic Union.

``It took about 10 minutes to fill out the form at the courthouse office,'' she said. ``I didn't mind paying the taxes for social work, but not to finance politics.''

Thomas Krueger, a spokesman for the Lutheran church, said loss of faith was usually behind the decision.

``I think the majority, although they still see themselves as Christians, feel that the church no longer has anything to say. That they say `We can get along without the church and we don't need it,''' Krueger said.