After years of marriage, you probably know not to talk to your wife before she's had her morning coffee and not to disturb your husband while he's watching Star Trek reruns. While you may have mastered all those day-to-day quirks, you and your better half may not know each other's retirement expectations.

A recent Fidelity Investments survey of couples aged 43 to 70 found that an alarming number of husbands and wives don't always agree on their plans and expectations for retirement.

  • Among more than 30% of couples, husbands and wives had completely different answers when asked about the age they plan to retire, what kind of lifestyle they expected in retirement, and whether they planned to keep working in retirement.
  • Only 39% of couples gave matching answers when asked which source of income would be their primary livelihood in retirement.
  • One in five couples couldn't even agree about whether they'd used a financial advisor to help them make their retirement plans.
  • Couples showed big gaps in knowledge when asked about when they could draw on their spouse's pension income, about their life insurance coverage, and about their Social Security benefits.

Here's the good news: couples who plan together may retire better. The few husbands and wives who jointly worked out their retirement plans were more prepared for unexpected events in retirement and more optimistic about their expected retirement lifestyle.

Planning for two
It's pretty easy to see how couples can slip off the same retirement page. In many families, spouses divide and conquer the household tasks, leaving one person in charge of financial planning (and the other person stuck doing laundry). Even if your dear husband or wife professes to be allergic to numbers, both spouses need to come to an understanding about a joint retirement plan.

Start by talking about everything except the numbers. Discuss the age at which you'd like to retire and the lifestyle you hope to have in retirement. Explore your individual and joint retirement ideas, whether that means working part-time, going back to school, traveling, or indulging all your hobbies.

Only then should you start bringing in figures and charts. Make sure both of you understand each other's retirement benefits and your life insurance. That means going through the details of your IRAs, bank accounts, brokerage accounts, annuities, pensions, workplace plans, and Social Security. Find out how much money each might provide and when it would be available.

Put it in writing
While you're digging through the details of all those numbers, it's a great time to put your plan to paper. Make some notes about the basics of your life insurance policy and your retirement benefits. Then lay out a plan for tapping into these sources of income. File this documentation with your other important papers.

Having a plan documented will help identify any holes, like whether you've budgeted enough for health care and whether your plan to start raising horses in retirement will bankrupt the family. It will also be invaluable if, heaven forbid, one of you meets an unexpected and untimely demise.

If you need help with the details of retirement accounts and planning, head to the Fool's Retirement Center to learn the must-knows and avoid the pitfalls. For help with more detailed aspects of planning, preparing, and living retired, take advantage of a free 30-day stroll through the Rule Your Retirement newsletter. Ask your sweetie to join you.

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Fool contributor Mary Dalrymple welcomes your feedback. The Motley Fool has a disclosure policy.