It's official: Union-managed multi-employer health insurance plans are getting a special exemption from an Affordable Care Act — also known as Obamacare — tax. To make up for the lost revenue, taxes are going up on other plans.

The rules change, first proposed by the White House earlier this month, was announced by the Health and Human Services Department on Monday evening. The change exempts “self-administered, self-insured group health plans” from the law's reinsurance fee.

The shift will raise the cost of the tax for those who do pay to $44 a year. It had previously been $42. In essence, the change is forcing those who don't get the exception to pay an extra $2 for those who do.

The phrase “self-administered, self-insured group health plans” would include multi-employer plans. These are also known as “Taft-Hartley plans” and are widely provided by organized labor groups to their members.

An administration official disputed to Fox News that the change was aimed “solely” at union plans. “This definition would exempt any self-insured group health plan that does not use a third-party administrator for claims processing or enrollment, not only union plans," the official said.

Big Labor had clamored to have its members' plans exempted from a ACA's reinsurance tax — a fee meant to reimburse insurance companies for the cost of accepting high-risk customers. Unions argued it was unfair penalty to their members for having won high-quality insurance through collective bargaining.

The proposed exception has drawn strong opposition from Republicans, who argue that the administration is simply giving union allies a special favor.