Eight years ago, Megy Karydes decided to walk away from her corporate job to embark on a new path as a freelance writer and marketing consultant. Karydes enjoyed being her own boss, working with her own clients and having the flexibility to set her own schedule.

But as Karydes built up her business, one thing fell by the wayside: investing in a retirement plan. Earlier this year, she met with her financial advisor and accountant to change that. Karydes set up what's often known as a solo 401(k) -- a 401(k) plan popular with self-employed individuals.

"I hadn't been investing consistently since I left my corporate job," she said. "I'm now in a position where I'm making more as an entrepreneur than I was making [in my last job], and not setting aside retirement funds was a huge financial mistake."

Saving for retirement without the help of an employer-sponsored retirement plan is a challenge facing many of the more than 14 million Americans who are self-employed. One survey found that 28% of self-employed people aren't saving for retirement, while many who do save rely on traditional savings accounts, meaning they miss out on the benefits of tax-advantaged retirement accounts.

But if you have money to set aside for retirement, there should be little stopping you from establishing a tax-advantaged retirement plan, said Mike Piper, a certified public accountant who runs the investing blog Oblivious Investor. Brokerage firms, he added, will walk you through setting up the account.

"It's not that hard at all," he said. "It'll take a little while to go through the paperwork, but it's not challenging."

Many people are already familiar with two of the options available to self-employed individuals since they're also widely used by workers who aren't self-employed: traditional IRAs and Roth IRAs. (Read more about them here.) But contributions for such IRAs are limited, and if you're self-employed and want to set aside more than what traditional and Roth IRAs allow, you have several tax-advantaged options.

Here are three of the most common retirement plans for the self-employed.

The solo 401(k)
A provision in 2001 tax-reform legislation gave rise to solo 401(k)s, which allow individuals to contribute to 401(k) plans in two capacities: as the employee and as the employer.

Under this framework, solo 401(k) plans allow most individuals to make higher contributions than they could through other self-employed retirement plans.

What also makes solo 401(k)s distinct from other self-employed retirement plans is that, like employer-sponsored 401(k) plans, individuals can choose either Roth plans or traditional plans.

With Roth 401(k) plans, contributions are not tax deductible. Once it's time to withdraw from the plan, however, distributions are tax-free. With traditional 401(k) plans, contributions are tax deductible but distributions are taxed upon withdrawal.

There are a couple of drawbacks to solo 401(k)s. Setting them up takes a little longer than it does with other plans. While other self-employed retirement plans can be opened with just an online application, solo 401(k)s usually require a few extra steps.

There's also a bit of deadline pressure. To contribute for a given year, you must open the plan during that calendar year, though contributions to the plan can be made as late as your tax return due date in the following year. For instance, an individual wishing to make a 2015 contribution to a solo 401(k) must establish his or her plan by Dec. 31, 2015, and can continue to make contributions to it until April 15, 2016 (or Oct. 15 if he or she has filed for a tax return extension.)

SEP IRAs and SIMPLE IRAs
SEP IRAs (short for Simplified Employee Pension) and SIMPLE IRAs (Savings Incentive Match Plan for Employers) follow the same rules as traditional IRAs but feature higher contribution limits.

For SEP IRAs, you can contribute up to 25% of your net earnings from self-employment or $53,000 -- whichever is lower.

For SIMPLE IRAs, as with solo 401(k)s, you can contribute both as an employee and an employer. However, the contribution limits are lower than those of solo 401(k)s.

Unlike solo 401(k)s, SEP IRAs and SIMPLE IRAs do not feature Roth plans, but one advantage is that they generally take less time to establish, and, as the latter plan's name suggests, they are indeed simpler.

In addition, SEP IRAs feature later deadlines than solo 401(k)s: You can wait until your tax return due date in 2016 to open (and contribute to) a SEP IRA plan that counts toward the 2015 tax year.

For SIMPLE IRAs, the deadline for establishing a plan is Oct. 1 of the calendar year for which you wish to make contributions. Employee contributions can be made up until Jan. 30 of the following year, while employer contributions can be made until the tax-return due date of the following year.

Find more information on self-employed retirement plans on the IRS' website here. And as with anything that may affect your taxes, it's a good idea to consult your accountant.

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