Most people nearing retirement don't realize what a critical decision they have to make when it comes to claiming their Social Security benefits.

It's all about timing, according to a report by Sunnyvale, Calif.-based Financial Engines. With thousands of claiming strategies out there to choose from, it isn't all that surprising that people don't understand their options. According to a survey by Financial Engines and Matthew Greenwald and Associates, 25 percent of respondents were confident in their ability to make a good claiming decision for their household – at the beginning of the survey.

By the end of the survey, one-third acknowledged that claiming Social Security is more complicated than they thought and four in 10 were interested in getting help.