3 Money Mistakes That Could Ruin Your Retirement

More than 40% of pre-retirees say running out of money during retirement is their greatest fear, and six in 10 older Americans are actually more afraid of spending their retirement stash than they are of dying. To avoid running out of cash, it's important to save as much as possible for retirement. It's also important to avoid mistakes that could undermine your efforts at financial security -- like these three big blunders that could ruin your retirement.

Colorful 401(k) letters next to piggy bank
Colorful 401(k) letters next to piggy bank

Image source: Getty Images.

1. Borrowing against your 401(k)

If you have high-interest debt or a financial emergency, your 401(k) balance may look like a nice source of funds to tap into. Unfortunately, taking a 401(k) loan is a risky gamble, because the entire unpaid loan balance becomes taxable if you can't pay back the loan on time.

The price for failing to repay a 401(k) on time can be devastatingly high: You'll owe state taxes, federal taxes, and a 10% withdrawal penalty on the outstanding balance. If you still owe $10,000 at the end of the repayment period, and you have to pay a 25% federal tax, an 8% state tax, and a 10% penalty, you'll pay a total of $4,300 in taxes.

You may plan to pay back your loan and avoid the tax consequences, but if you leave your job for any reason, then you'll suddenly have a narrow time frame -- usually around 60 days -- to repay the entire 401(k) loan. If you unexpectedly find yourself in the unemployment line, then you don't want to be forced to pay back a huge sum of money in order to avoid a big tax penalty.

Even if everything goes right and you pay back your loan on time, you'll still miss out on the investment gains you'd have made by leaving your money invested -- which could be substantial if the market is doing well. And when you repay the money you borrowed from your 401(k), you repay it with after-tax dollars as opposed to pre-tax contributions -- but you're still taxed on withdrawals as a senior. In other words, you'll be double-taxed on the amount paid back.

In a worst-case scenario where you never repay the cash at all, between the tax penalties and the forgone capital gains, your $10,000 loan could cost you over $40,000 over the course of 20 years (assuming your portfolio earned 7% per year). It's easy to see why a mistake like borrowing from your 401(k) could be a recipe for disaster.

2. Cosigning for your kids' student loans

As a parent, you want what's best for your kids. Unfortunately, if you help your children out by cosigning for student loans, you could put yourself at serious financial risk.