Millions of seniors today get a large chunk of their retirement income from Social Security, and while those benefits aren't designed to sustain seniors by themselves, they're crucial nonetheless. If you expect to rely on Social Security to some degree, then it's imperative that you take steps to avoid losing out on benefits. These mistakes, however, could really cause you to struggle during your golden years.

1. Not working a full 35 years

Your Social Security benefits are calculated based on how much you earned during your highest 35 years of wages. Those wages are adjusted for inflation, and then a formula is applied that determines how much money you're entitled to a monthly basis. The problem, however, is that if you don't work a full 35 years, you'll have a $0 factored into that average for each year you're without an income, and too many $0s could bring your benefits down.

Senior man and woman sitting at table with teacups in front them, both sporting serious expressions

IMAGE SOURCE: GETTY IMAGES.

The solution? Extend your career for a couple of years. In doing so, you'll replace some $0s with an actual income, thereby bringing your benefits up.

2. Claiming benefits too soon

The Social Security Administration (SSA) allows you to start collecting benefits as early as age 62. However, you're not entitled to your full monthly benefit based on your earnings record until you reach what's known as full retirement age.

That age isn't universal -- it's based on your year of birth, as follows:

Year of Birth

Full Retirement Age

1943-1954

66

1955

66 and 2 months

1956

66 and 4 months

1957

66 and 6 months

1958

66 and 8 months

1959

66 and 10 months

1960

67

DATA SOURCE: SOCIAL SECURITY ADMINISTRATION.

If you start taking benefits prior to full retirement age, they'll be reduced by 6.67% a year for the first three years you file early, and then by 5% a year for each year after that. This means that if you're looking at 67 as your full retirement age, claiming benefits at the earliest possible age of 62 will result in a 30% reduction.

Now some people assume that if they claim benefits early and face a reduction, they'll be bumped up to their full benefit once they reach full retirement age. Not so. The benefit you start out collecting is the same amount you'll receive for life, unless you manage to withdraw your benefit application within a year and pay back all the money the SSA gave you.

3. Not coordinating with your spouse

If you and your spouse both worked, and are therefore both eligible for benefits based on your respective earnings, then it pays to sync up and strategize on how to get the most money from Social Security. Some couples don't do that, however, and miss out on the chance to grow their benefits.

Just as you're allowed to file for Social Security before full retirement age, so too are you able to delay benefits past that point. For each year you hold off until age 70, you can get an 8% boost in benefits that remains in effect for the rest of your life. Therefore, if you and your spouse are both entitled to benefits, it often pays to have one person file at full retirement age, while the other person grows his or her benefits to snag that increase.

Sometimes, the higher earner will hold off on Social Security. Other times, the lower earner will wait to file. There are other strategies to play around with, too, but the key is to run some numbers and see what makes the most financial sense for you as a couple.

The last thing you want to do is lose out on income that could be critical to your retirement. Avoid the above mistakes, and with any luck, your benefits will help you enjoy your golden years to the fullest.