If you hire your spouse, even part time, you can deduct the cost of health insurance offered as a benefit. Sole proprietors and partners typically pay for health insurance out of their own pockets. They receive only a 60% credit on Form 1040, which also reduces the Schedule A medical deduction. Offered as an employee benefit, however, health insurance is a full expense that reduces company profit by the amount of the premiums.
Of course, your spouse must actually work to earn a salary. Presumably, you offer health insurance as a benefit to all employees, but even if you don't, you may be able to defend an exclusive offering. Length of service, temporary vs. permanent staffing, salary bonuses -- any of these might serve as reasonable grounds.
Check with your accountant on the details.
--Howard Scott is a business writer and small business tax preparer in Pembroke, Mass.