Another limit not listed here which we've never used but should be affected by in 2014: the "saver's credit" (AKA the retirement savings contribution credit) limit increases to $60,000 (from $59,000) for joint filers ($45K for HoH and $30K separate filers). If I understand it right (never studied it before), this means that for joint filers, the first $2000 per person of each spouse's contributions to IRA and 401K/403B plans receives a tax credit of anywhere from 10% to 50% of the amount saved depending on the specific AGI. This credit is calculated on Form 8880.
For example, if joint filers earning less than $35,500 (using 2013 limits) each contribute $2000 to such plans, 50% of the total contribution ($1000 each, or $2000 total) is a tax credit (or the amount of tax liability if less than $2000). Joint filers earning less than $35,500 probably owe less than $2000 in tax anyway, so they would basically receive a tax credit for the total tax due.
I think that's right. Has anyone here used this before? Am I close? If so, even in a low tax bracket it would be a no-brainer for each of us to contribute $2000 each since there is an instant ROI equal to the applicable percentage of your tax credit on what we contributed (10%, 20% or 50%). These would also reduce MAGI for ACA purposes, so it's a double-win.