As we discussed last week, the annual Medicare open enrollment period begins on Oct. 15 and runs through Dec. 7. If you’re on Medicare and you feel unhappy about your current coverage, you’re in luck—open enrollment is all about change. During open enrollment, you can switch from original Medicare to a Medicare Advantage plan, or vice versa. You can also change your Medicare Part D drug coverage. But Medicare can be tricky. Unless you are careful, you could end up in a less favorable situation. Here are four common Medicare pitfalls to avoid.

Pitfall #1: Failing to review your Annual Notice of Change. Some people assume their coverage stays the same unless they actively make a change. Unfortunately, that is rarely true. Insurance providers can change their terms of coverage every year, so you need to keep up to date on your plan benefits.

If you have a Medicare Part D plan, or if you are enrolled in a Medicare Advantage plan, your provider is required to send you an Annual Notice of Change at the end of every September. The ANOC informs you of changes to your coverage, including adjustments to premiums, out-of-pocket maximums, deductibles, coinsurance, your provider network, medication coverage, etc. If you have lost your ANOC, you can get a new one by contacting your insurance provider.

Pitfall #2: Losing your guaranteed-issue Medigap plan. Medigap coverage is supplemental insurance which helps pay for costs original Medicare doesn’t cover. When you first enroll in Medicare, insurance companies are required to issue you Medigap coverage without considering pre-existing conditions. But down the road, if you choose to enroll in a Medicare Advantage plan, you will lose your Medigap plan. You can’t have both. As long as you stay with a Medicare Advantage plan, that isn’t a problem. But what happens if you ever decide to go back to original Medicare? In that case, you may have to go through full medical underwriting for Medigap coverage — meaning the insurance company will consider your pre-existing conditions and may refuse to cover you. The key takeaway: before switching to a Medicare Advantage plan, make sure you really like their coverage. It may be a one-way ticket.

Pitfall #3: Delaying Medicare enrollment when your job insurance is secondary. This isn’t an “open enrollment” pitfall, but something to keep in mind. If you’re over 65, still working, and still covered by your employer’s health plan, you need to know if your employer’s plan provides primary or secondary coverage.If your company has 20 or more employees, the plan probably provides primary coverage. However, if your company employs fewer than 20 people, Medicare often becomes the primary insurer for employees over age 65. If your company’s health plan is secondary, you must enroll in Medicare. Failing to enroll means you are uninsured, and the consequences can be catastrophic if you get in an accident or become seriously ill.

Pitfall #4: Missing the annual open enrollment period. From time to time, I talk with people who panic because they missed the open enrollment period. I usually tell them to relax. Open enrollment is only crucial for those wanting to move from original Medicare to Medicare Advantage (or vice versa), or who want to change their Part D drug coverage. If you want to make those changes and miss the open enrollment window, you are probably out of luck. There are exceptions if you have a qualifying life event (see Medicare.gov for more on that). Otherwise, you’ll have to wait until next year’s open enrollment to make changes.

Here’s some good news. You can make changes to Medigap coverage anytime, though you’re usually required to go through a medical exam. And if you want to change between Medicare Advantage plans, you can do that in the Medicare Advantage open enrollment period, which runs from Jan. 1 to March 31.

One final point about Medicare. Some people assume they can’t afford Medicare Part D drug coverage. This is where Medicare’s “Extra Help” program comes in. Extra Help assists those with limited means to pay for Part D. If you are on full MediCal coverage, or if you are receiving Supplemental Social Security Income benefits, you will likely qualify automatically. You can find more information about Extra Help at Medicare.gov.

Steven C. Merrell is a partner at Monterey Private Wealth, Inc., a Wealth Management Firm in Monterey. He welcomes questions that you may have concerning investments, taxes, retirement, or estate planning. Send your questions to: Steve Merrell, 2340 Garden Road Suite 202, Monterey, CA 93940 or email them to smerrell@montereypw.com.