A common piece of advice is to max out your pre-tax 401(k) while you work. You'll get a tax break now and then pay taxes on the money during retirement when you'll be in a lower tax bracket.

But, is that actually true?

For those of you who pay attention to how much gets deposited into your checking account from your paychecks, you may have noticed that your pay randomly goes up at some point during the year.

There's a good chance it's due to Social Security.