Hedge fund managers including billionaire John Paulson won’t immediately face new limits on their use of insurance in offshore tax havens, after the IRS proposed rules and chose not to make them effective now.

The Internal Revenue Service rules, released on Thursday, will take effect only after the agency takes comments and considers how several important terms will be defined.

The U.S. Treasury Department said in an Aug. 9 letter to then-Senate Finance Committee Chairman Ron Wyden that it was concerned about a “loophole” that allows hedge fund managers to limit their personal income tax bills by routing investments through insurance companies in low-tax jurisdictions.

Lindsey Held, a spokeswoman for Wyden, an Oregon Democrat, called the IRS announcement a “good first step in enforcement.”

In 2012, top executives at Paulson’s hedge fund invested $450 million in a Bermuda-based reinsurer they’d set up known as Pacre Ltd. It has no employees, sells less insurance than industry norms, and invests almost exclusively in Paulson hedge funds.

Hedge fund manager Dan Loeb helped establish Third Point Reinsurance Ltd. in Bermuda, and David Einhorn’s Greenlight Capital Re Ltd. is based in the Cayman Islands. Representatives from Third Point Re and from Validus Holdings Ltd., which is a minority investor in Paulson’s Pacre, declined to comment on Thursday.

Short-Term Gains

Ordinarily, hedge fund managers’ profits from trading are taxed as short-term capital gains at rates of up to 43.4 percent, plus state taxes. Insurance companies only have to pay taxes on their reserves when sold, giving the hedge fund investors the ability to defer taxes and pay at the lower rates -- 23.8 percent -- that apply to long-term capital gains.

The notice from the IRS doesn’t use the word “loophole” and doesn’t invoke the agency’s authority to immediately stop what it sees as abusive transactions. Instead, the notice said the government is trying to “clarify” when “purported” reinsurance companies are really in the insurance business.

The IRS asked that comments be submitted within 90 days.