Moneybox's Paul Lewis points out on Twitter [2] an interesting quirk of the Marriage (Same-Sex Couples) Bill: when it comes to pensions, it's not entirely equal.

Paragraph 123 of the explanatory notes reads [3]:

Paragraph 18 of Schedule 9 to the Equality Act 2010 provides that it is not discrimination because of sexual orientation to restrict access to a benefit, facility or service that would be available to a person who was married, to someone who is in a civil partnership in relation to rights accrued before 5 December 2005 (the date the Civil Partnership Act came into force). This means that an occupational pension scheme as a minimum only has to provide survivor benefits to civil partners on rights accrued since that date. Paragraph 15 removes the word married from sub-paragraph (1) and inserts a new sub-paragraph (1A) in paragraph 18 of Schedule 9 to the Equality Act 2010. This extends the exception so that it also applies to same sex couples in the same way as to civil partners.

That is: if you are married to someone of the same sex, your marriage is qualitatively different in at least one (potentially very important) way. Any pension benefits accrued before 5 December 2005 are allowed to continue to ignore same-sex marriages.

The reasoning behind the rule is obvious. When pension funds were estimating the costs of providing couples' benefits, a small but significant part of the estimation will have been based on the fact that any gay members of the pension plan would never be able to claim those benefits. When civil partnerships were introduced, it was decided it would be more trouble than it was worth to force those funds to treat civil partnerships as marriages; and now, since the Marriage (Same-Sex Couples) Bill is essentially just a provision for changing the name of civil partnerships, the same rule is being carried over.

It's important to note that the rules are just the minimum, so most pension funds will presumably do the right thing and cover married couples equally regardless of gender. And obviously eventually the difference will be moot. But the desire to take the easy way out may end up hurting a few couples just when they're at their most vulnerable. Hopefully an amendment will change this rule and restore equality to equal marriages.