Many Americans are "unretiring".

• Position: Working after retirement and its benefits

There once was a time when retirement meant leaving the workforce for good. However, a survey by Zogby International and the MetLife Mature Market Institute found that about 11% of retirees ages 55-59, 16% between 60-65, and 19% between 66-70 report they have gone back to work.

Doing so is not necessarily a negative. Not everyone does it because they are having trouble making ends meet. Some return because they are bored and need a new challenge; others find a great opportunity to share a lifetime of skills. Yet, for every retiree who considers a return to the workplace, there is a critical need to review investment, insurance, and tax issues. If a retired person has not already done so, it makes sense to confer with a tax or financial advisor before going back on the clock.

Here are some critical points from the Financial Planning Association, Denver, Colo., to consider in a working retirement:

Be sure a working retirement is a variable in your planning. If you are in your early 50s and reviewing your retirement planning so far, it makes sense to ask yourself under what conditions you would return to the workplace.

Consider how a return to the workplace will affect you personally and socially. If you are 40, 50, or 60, working probably feels like breathing--when have you not worked? However, it may not be the best option after a year or two out of the workplace.

Talk to a tax professional before you make a move. Tax issues should not determine your ambitions and goals, but it is important to consider the impact work-related income will have on your retirement. Many retirees find that it does not take much post-retirement, work-related income to tip them into a higher bracket. Look for ways to control the taxes you ultimately will pay, including continued participation in qualified plans, IRAs, and other tax-favored accumulation...