Retirement planning seems straightforward until you realize how many ways it can go wrong. Financial advisors see the same costly mistakes over and over again — errors that can easily cost retirees six figures or more.

Find Out: I’m a Financial Expert: This is the No. 1 Mistake Americans Make With Their Roth IRAs

Read Next: 8 Common Mistakes Retirees Make With Their Social Security Checks

Here are the biggest retirement blunders that could derail your financial future. Pay close attention and save a bundle!

These mistakes could really mess things up from the start.

“If you spend more than you earn, your future retirement savings shrinks,” explained April Taylor, financial coach and founder of Jr. Moguls.

This isn’t just about fancy cars or expensive vacations. Instead, it’s about consistently spending more than you bring in, which makes it impossible to save properly for retirement.

Learn More: Avoid This Retirement Savings Mistake That’s Costing Americans Up To $300K

Taylor shared that “time is your biggest asset — the earlier you start contributing to a retirement plan, the more opportunity you have for your money to grow.” She added that even small, consistent contributions can build into six figures over time.

For self-employed individuals, this delay is particularly costly. Gina Stoddard, chief of staff at Broad Financial, said entrepreneurs who stall on starting retirement accounts “can miss out on nearly $30,000-$150,000 a year depending on their income over the course of their career.”

“Inflation is inevitable, and rising costs must be factored into your retirement plan,” Taylor said. In other words, if your money isn’t growing, it’s losing value. That can be a real shocker when it’s time to retire.

With these mistakes, if one thing goes wrong, they could really cost you.

Stoddard warned about being “overly concentrated in Wall Street products and traditional equities.” She explained that “your savings can possibly undergo a dramatic dip if the stock market descends.” The potential cost of failing to diversify? “Upwards of $100,000+,” she said.

“Alternative investments are a proven method to achieve diversification, as their value typically works inversely to the public market,” Stoddard noted. She mentioned that self-directed retirement accounts can invest in real estate, precious metals, private businesses, creative pursuits and more.

Story Continues

Retirement can have a 20- to 30-year time horizon, said Bethany Dever, vice president and relationship manager at Rockland Trust. She explained that “moving too much of your assets to bonds or cash (80%-100%) too early in retirement in the hopes of protecting your nest egg can cause damage to your long-term goals due to underperformance.”

Potential cost to a $1 million portfolio: $500,000 to $1.2 million in potential growth.

Taxes and other legal matters can get more complicated in retirement, so you’ll want to make sure to avoid these mistakes.

“I worked on a case where the ex-spouse received $250,000 from an IRA because the beneficiary designation had not been updated when the divorce occurred,” said Seann Malloy, founder and managing partner at Malloy Law Offices.

He added that it’s important to periodically revisit and ensure these designations remain “in harmony” with your estate plan.

Malloy explained that clients often don’t understand that drawing particularly large sums from tax-deferred plans can push them into higher tax brackets. He gave an example: “A $100,000 withdrawal could incur $30,000 in taxes if it kicks your income into the 32% bracket.”

Stoddard warned about prohibited transactions in self-directed IRAs, which “could potentially trigger immediate taxation on the full amount within your IRA, plus withdrawal penalties.” She estimated this could result in a loss of about $50,000-$100,000 in taxes.

Social Security and healthcare are incredibly important in retirement, so make sure you have those ducks in a row.

Dever shared that claiming at age 62 instead of waiting for full retirement age can reduce monthly benefits by up to 30% permanently. She also pointed out that “for every year you delay claiming Social Security past your FRA, you get an 8% increase to your benefit.”

Potential cost: $100,000-$300,000 in lost lifetime benefits.

Taylor warned that “ailing to plan for healthcare in retirement can quickly drain your savings. Dever cited a Fidelity study showing that “a 65-year-old couple retiring today will need $330,000 for healthcare expenses in retirement.”

Potential cost: $300,000

Retiring doesn’t include just taking out your money whenever you want. There are good and bad ways to do that.

Cashing out of your 401(k) early can be a costly mistake. “Not only will you incur penalties and taxes now, but you’ll also impact your future retirement by reducing the time your investments have to grow,” Taylor said.

Both Stoddard and Dever emphasized the costly penalties for missing RMDs. “If you miss the deadline to withdraw your RMDs, you could be fined with a 25% penalty of the missed allotted withdrawal amount,” Stoddard explained. This could range anywhere from $10,000-$50,000.

Dever referenced the 4% rule, explaining that “having a more than 4% distribution rate early on can cause a depletion of assets later in retirement.”

Potential cost: Running out of money five to 10 years early.

A retirement without a strategy is not the retirement you want.

Heath Harris, founder of Compound Advisory, spoke about one of his clients who sold an HVAC business without tax planning. It was a mistake. “Between federal capital gains, NIIT and state taxes, he paid close to $3 million straight to the IRS,” he said. With proper planning, Harris estimated they “could’ve saved him about $1.7 million.”

The moral of the story? It might be smart to seek expert help from, well, an expert. (This is especially true when dealing with large sums of money.)

More From GOBankingRates

This article originally appeared on GOBankingRates.com: I’m a Financial Advisor: 15 Retirement Mistakes That Could Cost You $100K or More