This period lasts for six months and begins on the first day of the month in which your client is both 65 or older and enrolled in Medicare Part B.

If your client times out on his Medigap open enrollment period, he may be charged a higher rate or denied coverage if he decides he wants a Medigap policy later.

3. Don’t pay more in high-income premiums than is necessary.

Higher-income beneficiaries pay higher premiums for Part B and Part D. It’s important to make sure your clients don’t overpay.

Social Security uses the most recent federal tax return provided by the IRS to determine who must pay higher Medicare premiums, typically the return from two years ago. But if your client retires this year, his income may be lower than it was when he was working. Social Security will bill him for a higher premium based on his prior income, unless he requests a new decision by filing form SSA-44.

You also may be able to use income and asset planning to keep client income below the graduated thresholds that trigger higher premiums.

4. Don’t make Medicare “couples mistakes.”

Couples mistake No. 1: Making poor choices about how to cover a spouse or dependent. Your clients who cover their families through an employer plan need to arrange for how their family will be covered if they drop that plan to enroll in Medicare. It’s important to study all the available options. For example, a plan through a state health insurance marketplace may be significantly less expensive than COBRA coverage.

Couples mistake No. 2: Spouses signing up for the same Medicare plan. After decades of sharing the same employer health plan, couples may do better to “split up” when it comes to Medicare. Because each spouse has individual health-care needs, the most cost-effective coverage for one spouse is not likely to be the most cost-effective option for the other. Medigap plans can be an exception: Couples may be able to get a household discount if one of the standardized plans works well for both of them.

5. Choose Medicare plans carefully.