• To be eligible to contribute, the couple must be legally married at tax year-end and file taxes jointly. The couple's combined earned income must equal or exceed the combined IRA contribution.

• Contributions can be made to traditional IRAs as long as the owner is under age 70 1/2, while there is no age limit for Roth IRAs.

• In 2008, the maximum contribution to an IRA is $5,000 with an additional $1,000 catch-up contribution for individuals age 50 and over.

• For traditional IRAs, if the working spouse is covered by a qualified retirement plan but the nonworking spouse is not, the contribution for the nonworking spouse is phased out once adjusted gross income (AGI) is between $159,000 and $169,000 in 2008 and totally phased out once income exceeds $169,000. If you both have earned income equal to at least the maximum IRA contribution amount and are both covered by a qualified retirement plan, your contribution is phased out at joint AGI between $85,000 and $105,000 in 2008. If neither of you is covered by a qualified plan, both of you can make a deductible contribution regardless of your AGI.

• For Roth IRAs, eligibility is phased out for AGI levels between $159,000 and $169,000 in 2008. It doesn't matter whether your spouse is covered by a qualified retirement plan at work.

Contributing to a spouse's IRA may be as beneficial to the working spouse as to the nonworking spouse, since the assets are likely to be shared during retirement.