Changing jobs could cost you money if you don't do it right. 

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While it may appear like an easy task to switch jobs, career experts caution there is a multitude of choices you need to make before and during your job switch, choices that can end up costing you thousands of dollars if not done right.

“Like any major life transition, switching jobs can be a really stressful time in anyone's life,” said Richard Castellini, vice president of consumer marketing at Careerbuilder.com “You need to plan way ahead of your actual leave date to make sure everything is taken care of. Or else, it can bite you in the wallet.”

The first thing you do when you get a formal offer from your new employer is nothing, experts said.

Some employers fire resigning employees on the spot. Also in today’s digital age, resigning employees’ actions are sometimes tracked to make sure they aren’t stealing company information.

To prepare for the worse, you should begin gathering things at your job before you give your resignation--projects, documents, presentations--anything that you may need and put them aside. If things go badly with your resignation, you’ll have access to your  work beforehand.  

Don't steal company propriety or intellectual property, however.

“You’re making sure you have your sales contacts or the research you collected that will make you productive at your job,” said Roberta Matunson, president of Human Resources Solutions in Northampton, Mass.

Also, experts said you should take advantage of your current employers benefit package before your final day at work--most importantly your medical, dental and vision benefits.

“The goal is to maximize the benefits at your outgoing employer,” said Castellini of Careerbuilder.com. “Your future employer could have benefits that don’t start for three, six or even nine months.”

It is possible to request your outgoing employer to keep of your current benefits until your new ones kick in, but it’s not guaranteed. Also take advantage of your tax-free benefits that you’ve set aside like your health flexible spending accounts.

There are also your 401(k) and retirement plans to think about.

Unless an employees’ 401(k) is below the employer’s minimum balance requirements, it’s best just to leave your 401(k) retirement cash alone, experts said.

“The 401(k) is usually a person’s number one mistake when they change jobs,” Castellini said. “Often people will cash their 401(k)s in, or try to roll it over before they know what they want to do with it. That’s just asking for tax trouble.”

Cashing in a 401(k) or improperly rolling a 401(k) over can cost an employee dearly. The IRS charges a 10% penalty to cashed out 401(k) before retirement age. You will also be taxed on that 401(k) distribution like income. 

Casttellini said that it’s possible your new employer may not have as many choices to invest as your old employer. If your 401(k) is of a sufficient size, then you can often leave your funds with your current employer.

“Worry about your 401(k) after you get settled,” he said. “You’ll have a better idea of what you want financially after you get everything else taken care of. The 401(k) is the last thing you should worry about.”

There might be tax deductions that can come with taking a new job, especially if you’re moving to an out-of-state job.

The IRS allows a deduction for moving expenses under certain circumstances, experts said. That can include everything from storage, to the movers, to the $4/gallon gas you’re about to pay to drive your car across the state. There’s also the possible deduction of new clothes for the start of your new job under certain circumstances.

While many employers offer to reimburse employees for moving expenses, if you didn’t negotiate for that benefit beforehand when you took your offer, you can always deduct it on your taxes.

Finally, make sure you close down your work at your current job properly. Often employers will have projects they want employees to finish up quicker than others. The goal is to make sure the transition from you as the employee to the person who takes your spot is as seamless as you can make it. 

"Try to have a transition meeting with your immediate supervisor," Castellini said. "You want to make sure your relationship with your employer remains a good relationship. You'll see these people again.  You don't want to leave a sour taste in their mouths."