GM recently began offering expanded health care coverage and benefits to same-sex married couples.

When General Motors began extending health care insurance to same-sex married couples on Oct. 30, it basically brought the automaker on par with many of its competitors.

Married same-sex GM workers can now add spouses to their health care plans at any time “within one year from their date of marriage or during the next annual enrollment period with proof of a valid, legal marriage license,” GM said in a statement.

Ford Motor Co., Chrysler Group, American Honda Motor Co., Nissan North America, Subaru of America, Toyota Motor Sales and Volkswagen Group USA also provide employees with same-sex domestic partner benefits.

The big change is recognizing same-sex marriages on par with traditional marriage, including the elimination of some tax penalties.

“We’ve been offering benefits to same sex partners since 2000,” said Jay Cooney, Ford spokesman. “We began formally recognizing marriages for tax purposes since the Internal Revenue Service ruling in August.”

Chrysler did the same in September.

GM’s policy change recognizes same-sex marriages regardless of the state of residence, and allows lesbian, gay, bisexual and transgender (LGBT) employees to buy health care insurance for their partners without a tax penalty. Pension and savings plans are also included.

GM said the decision does not change the benefit plan and policy rules covering same-sex domestic partners, which have been since 2000, just like Ford and Chrysler. Before the changes, employees had to sign an affidavit proving that they share, among other things, finances and residency.

Thirteen states and the District of Columbia allow same-sex marriages. In June, the U.S. Supreme Court overturned the Defense of Marriage Act, which denied same-sex couples federal benefits available to heterosexual couples.

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According to the Human Rights Campaign Foundation’s Corporate Equality Index 2013, automakers are among the top companies in the U.S. providing benefits, insurance and at implementing programs to protect the rights of LGBT employees.

The four automakers mentioned all achieved perfect scores – 100 points on a 100-point scale – this year. Subaru received an 85 while Nissan achieved a score of 75 points. No other automakers with U.S. operations were listed and participation was voluntary.

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Subaru’s score was lower due to the fact that it lacked some “soft” benefits for partners as well as not offering transgender-inclusive health insurance coverage. Nissan was docked for the same reasons, plus it was lacking company-wide organizational competency programs.