Thanks again. I've been doing more reading in the meantime, and I did find 35(f)(1), but I also found more ambiguous references to which plans can be deducted:
IRS Notice 2008-1 suggests that this deduction may only be available if the plan is established under the trade or business (see also IRS Publication 502).
Interesting but not applicable: IRS Memorandum [social security number removed] clarifies that a sole proprietor may deduct premiums for a policy issued in their own name rather than the name of the business. Memorandum [social security number removed] clarifies that deduction of Medicare premiums is permitted for self-employed individuals.
Since my wife is on a plan through my employer, it seems like maybe the deduction if over 10% AGI is the only option? Obviously, I'd prefer the straight ahead deduction from her business income (with no 10% limit).
