As the Obama administration tries to stop companies from avoiding taxes by moving their headquarters overseas, the makers of some of the world’s most lucrative and expensive medicines are using another tactic to reduce their payments to the government.

Take the case of Gilead Sciences, which has come under severe criticism for the high cost of its in-demand new hepatitis C drug, Sovaldi, which sells for $1,000 a pill, or $84,000 for a typical course of treatment.

Although Gilead, the developer of Sovaldi, is a U.S. company based in Foster City, California, the patent rights have been transferred to an Irish subsidiary. So Gilead’s profits from the booming sales of Sovaldi are taxed at Ireland’s rate, which is well below the American one.

Big pharmaceutical companies have done this for decades, as have some technology companies. Now biotechnology companies are following suit.

Transferring individual products is not as advantageous, tax-wise, as moving the company’s official headquarters, which is known as an inversion. Pharmaceutical companies, including Pfizer, AbbVie, Actavis and Mylan, have been particularly active recently in pursuing this inversion strategy, and President Barack Obama is trying to rein it in.

But for many biotech companies, the transferring of product rights is providing a substantial tax benefit. That’s because the true value of a drug lies in its patent — which protects it from competition and allows it to be sold at a higher price.

Alexion Pharmaceuticals has said that as of this year, certain intellectual property for Soliris, its super-expensive drug for rare diseases, is being held in Ireland, where it has established certain operations.

Regeneron Pharmaceuticals has made Ireland the tax base for foreign sales of its big-selling eye drug Eylea and for some drugs still in development like the powerful cholesterol-lowering medicine alirocumab.

A sign of the times: Regeneron recently agreed to pay $67.5 million to BioMarin Pharmaceutical for a voucher that will entitle the cholesterol drug to a faster review by the Food and Drug Administration. Although Regeneron is based in Tarrytown, New York, and BioMarin in San Rafael, California, the transaction was between the Irish subsidiaries of the two companies.

BioMarin earned the voucher as a reward for developing a drug for a rare childhood disease. The drug, Vimizim, which treats an enzyme deficiency called Morquio A syndrome, will eventually be manufactured mainly in Ireland, the company has said.

The companies in general declined to be interviewed about their taxes. But in written statements some said that they complied with the law and provided jobs and valuable medicines to Americans.