When you're married, it's not just your own needs you're considering when planning for retirement. You also need to think about what your spouse wants out of his or her golden years. But what happens when you and your spouse have a sizable age gap to contend with? You might land in a scenario where one of you is ready to retire and the other could easily spend another half-decade or more in the workforce. And it's hardly an uncommon set of circumstances -- nearly 20% of U.S. married couples have at least a six-year age gap between them, according to the Census Bureau. If you're one of them, here are a few retirement-planning tips that might help.

1. Align on Social Security

When you're married, you have different options to play with on the Social Security front, and your decisions will likely hinge on how much you need that money and whether you and your spouse are each entitled to your own set of benefits. If, for example, you worked but your spouse didn't, he or she can still collect spousal benefits based on your work record -- but those benefits won't kick in until you file for your own benefits. That's not necessarily a bad thing, though, if you're the older spouse.

Older couple embracing at the beach


At the same time, if you and your spouse both worked, you can stagger your respective benefit claims so that you're growing one set of benefits for a higher payout. Whenever you delay Social Security past full retirement age (which is 66, 67, or somewhere in between, depending on your year of birth), you boost your benefits by 8% a year up until you turn 70.

So let's say you're 66 and your spouse is 60. You could file for benefits today and collect them in full, but if you want your spouse to be able to retire before his or her full retirement age, which is 66 and 10 months, you might decide that you'll hold off on filing for four more years and snag your maximum benefit. Then, if your spouse decides to retire at 64, he or she will take a hit on Social Security if he or she files for benefits immediately, since he or she won't have reached full retirement age. But, the 32% boost to your benefits might offset that reduction, thereby enabling you to retire just four years apart.

This is just one example of how you might work Social Security to your advantage. The key is to strategize with your spouse and see how those benefits might help you bridge that age gap for retirement purposes.

2. Be strategic about Medicare

Medicare eligibility kicks in at age 65, and if you're without health coverage at that point, it absolutely pays to sign up -- especially since enrolling late could cause your Part B premiums to go up. Remember, though Medicare Part A, which covers hospital care, is free for most enrollees, Part B, which covers doctor visits and diagnostics, costs money.

On the other hand, if you're the older spouse and decide to retire at 65, you don't necessarily need to sign up for Medicare right away. If your younger spouse is still working and has access to a group health plan through his or her job that you're entitled to participate in, you can hold off on enrolling in Medicare and you won't have to worry about a Part B penalty.

Why would you choose your spouse's health plan over Medicare? For one thing, it might cost you less if its premiums are heavily subsidized. Additionally, that group plan might offer a wider scope of coverage, thereby lowering your out-of-pocket costs as a participant.

Keep in mind, however, that because Medicare Part A is free, it generally makes sense to enroll once you're eligible. If you have a group health plan, Part A will act as your secondary insurance so that if there's something your primary plan won't cover, you can try running your claim through Medicare.

3. Seek some company if you're retiring first

When you're significantly older than your spouse, you might be driven to retire many years before he or she is ready. And while there's nothing wrong with that, before you go that route, make sure you'll have other people around for social purposes so that you're not bored and lonely during the day while your spouse is at the office.

Retirees are 40% more likely to suffer from depression than folks who work, and that often stems from feelings of restlessness and isolation. If you don't have friends or colleagues who are retiring when you will, you might consider holding off a bit, or seeing if your employer might approve a phased retirement where you decrease your working hours year over year rather than go from full-time to nothing at all.

A large age gap between you and your spouse can pose some problems on the retirement-planning front, but it doesn't have to. Just keep it in mind as you navigate your options and devise a plan that serves both of your needs.