You'll probably end up relying on Social Security to pay the bills in retirement, at least to some degree. As such, it's important to get as much money out of it as possible. But these less obvious mistakes could actually leave you with a much lower monthly paycheck from Social Security -- for life.

1. Not working a full 35 years

Your Social Security benefits are based on your personal earnings history -- specifically, your wages earned during your 35 highest-paid years on the job. But if you don't work a full 35 years, you'll have a $0 factored in for each year you go without an income. Many people don't know about this 35-year formula, so it's easy to see how a lot of seniors might retire before putting in that many years on the job. But if you want a higher benefit, you may need to be prepared to extend your career.

Older man at desk typing on computer keyboard

Image source: Getty Images.

2. Not checking your earnings statements for errors

Each year, the Social Security Administration (SSA) issues individual earnings statements. Each of those statements will contain your taxable wages for the year for Social Security purposes, as well as an estimate of your future retirement benefit. If you're at least 60, your earnings statement will arrive in the mail. If you're younger, you'll need to create an account on the SSA's website to access it. But no matter how you manage to get a hold of that document, it's important to review it for mistakes. If you have an earnings statement that's missing wages, for example, it could result in a lower monthly Social Security benefit later on.

Many people don't realize that earnings statements can contain errors, and so they neglect to give them a read. But ignoring that important document could really cost you. Furthermore, younger workers may not realize they can access those statements or that they even exist, so if you don't remember ever having gotten one, go ahead and create that account so you can look yours up.

3. Filing for benefits when you sign up for Medicare

Medicare eligibility begins at age 65, and when you go onto the SSA's website to sign up for it, you'll actually be asked if you want to sign up for Social Security as well, or Medicare alone. It's this very prompt that may cause some people to start claiming Social Security earlier than expected. But if you sign up for Social Security at age 65, you'll automatically shrink your monthly benefit for life.

You're only entitled to your full monthly benefit based on your wage history once you reach full retirement age, which is either 66, 67, or somewhere in between, depending on when you were born. But it's easy to get confused and go ahead with your Social Security filing in conjunction with your Medicare enrollment, so be aware of when your full retirement age is and wait until then if you want your full monthly benefit.

Social Security has a lot of rules, and knowing more of them could help you avoid needlessly reducing your benefits. Be sure to avoid the above mistakes, because while they may seem innocent, they could really end up hurting you financially in the long run.