[NickM]

Right, exactly. And besides the examples you mentioned, the differing income tax brackets on married couples is also a big example of this. If only one spouse is working, and the second spouse is deciding whether to get a job, then having all of the second spouse's income taxed at a higher marginal rate from the get go can easily influence people's decisions.

[gamblor956]

Note: for married couples, the tax bracket thresholds are doubled, except for the highest (37%) bracket, which kicks in for couples making more than roughly $625k but for singles at roughly $520k.

The actual effect is that you need to actually have a huge wealth disparity between partners' earnings for the so-called marriage penalty to kick-in. Fox News notwithstanding, the overwhelming majority of married couples will not see a marriage penalty.

[NickM]

All true, and good points. However the marriage bonus for single earners is much greater than the bonus for double earners, so if you look at it from a certain angle there is sort of a penalty for dual earners vs sole breadwinner marriages.