(Editor's note: This is the first in a series of weekly columns on retirement by Jim Cramer, founder of TheStreet , and Wally Konrad, former senior editor for Smart Money magazine.)NEW YORK ( TheStreet) -- Income. It's the holy grail of retirement and there's not much of it. Master limited partnerships are a nice exception. Their yields of 6%-plus look fabulous compared to anemic Treasury bond and CD rates. No wonder they're attracting retirement investors in droves. Unfortunately, there's a catch. MLPs can be a great retirement investment but a terrible retirement account investment. Put an MLP in your IRA or 401(k) and you'll miss out on some great tax breaks. What's more, you might get charged with additional taxes you weren't expecting. Here's the good news. MLPs don't pay corporate taxes. Instead, taxes are considered "pass through," meaning liabilities and expenses are passed on to investors. MLP investors may write off partnership expenses -- depreciation, etc. -- against income on their tax returns. Quarterly income distributions from an MLP are often considered a "return of capital," which means no taxes until the investor sells the MLP. What's more, there's still plenty of growth potential left for MLPs. Here's the not-so-good news. These breaks aren't allowed if the MLP is held in a retirement account. "If you put an MLP in an IRA or your 401(k), which is already tax advantaged, you miss out," says Mary Lyman, executive director of the National Association of Publicly Traded Partnerships. Here's why MLPs have a good news/bad news story. Like a limited partnership, an MLP is a business conducted by two or more lead partners and several other partners acting as investors. Unlike most limited partnerships, MLPs trade "units" on an exchange. In order to be considered an MLP, the partnership must earn 90% of its revenue from activities relating to natural resources, commodities or real estate. Most MLPs these days concentrate on transportation and storage of oil and natural gas. That big jolt of yield comes from the fact that MLPs pass cash flow onto a steady stream of income for investors. That structure is also what gives MLPs their tax advantages and why they don't work so well with retirement accounts.