Enrolling in Medicare can be stressful and confusing, but delay signing up and it can also set you back a bundle. Late enrollment penalties can hike a monthly premium by 10 percent or more – for the rest of your life.

More than 750,000 Medicare beneficiaries have made that mistake, boosting their Part B premiums, on average, by 30 percent, or an extra $440 a year. The problem is getting worse, too. With more people working past their 65th birthday and still getting health care coverage through their employers, they may not ask about Medicare until they miss their deadline.

Now a bipartisan bill introduced in Congress last month aims to reduce the number of seniors who get caught in that expensive trap – by simply telling people when to sign up.

More than 10,000 baby boomers turn 65 every day and become eligible for the federal insurance program that covers both seniors and the disabled, according to the Medicare Rights Center, a nonprofit national advocacy group. Most retirees, when they sign up for Social Security, are automatically enrolled in Medicare Part A, which pays for inpatient hospital care and rehab in a skilled nursing facility or nursing home.

Medicare Part B isn’t an automatic thing, however. Though optional, this is the plan that covers medical services that people need more often, such as doctor visits, outpatient hospital services, x-rays, lab tests and mental health care.

Most boomers celebrating their 65th birthdays this year will pay about $122 a monthfor Plan B coverage if they enroll three months before or after their birthday. Even if they’re still working, it’s up to each person to enroll within the window of eligibility or risk hefty surcharges, significant gaps in coverage and lack of access to health services.