Deciding when to file for Social Security is no simple task, and most Americans don't handle it well. But increasingly, help is available from an unexpected source: their employers.

The nation's largest independent investment advisory firm is rolling out a service today that walks 401(k) plan participants through their Social Security claiming options, with the aim of helping them maximize benefits. Financial Engines, which works with company retirement plans, will show participants how to integrate their Social Security income plan with drawdown from retirement savings. The service includes an online tool and optional one-on-one guidance from advisors.

This isn't the first service of its type, but Financial Engines' large presence in workplace plans means the service will be available immediately to 9 million 401(k) savers. Meanwhile, a more limited free version of the Social Security claiming tool -- lacking integration and one-on-one advice -- is available on the company's Web site.

Integrating robust Social Security planning tools into 401(k) plans is a positive development. Social Security is the most important retirement benefit for most Americans, but most of us leave big dollars on the table in lifetime income by failing to pick the optimal filing strategy.

“Coordinating 401(k) savings with Social Security is a big part of the retirement planning puzzle,” says Brooks Herman, head of data and research at Brightscope, which ranks and analyzes 401(k) plans. “More companies will be moving into this space - there’s a real need for robust tools.”

Timing is the key issue in Social Security claiming decisions. Benefits are calculated using a formula called the primary insurance amount, or PIA. Claimants who wait to start Social Security until their full retirement age (currently 66) receive 100 percent of PIA; taking benefits at 62, the first year of eligibility, gets them 75 percent of PIA. By waiting until age 70 (the maximum year for delayed filing credits), they'll receive 132 percent of the PIA. And those benefits are enhanced by an annual cost-of-living adjustment, which is added in for years of delayed filing.

Filing later means higher annual income for life, which can be a great hedge against the risk of running out of money in old age. Couples can boost their combined benefits further by executing a file-and-suspend strategy.

Nobel Prize winner and Stanford University professor emeritus William F. Sharpe is well known among financial advisors. He is one of the originators of the Capital Asset Pricing Model and co-founded Financial Engines in 1996 "with the purpose of making the kind of expert investment advice and portfolio management previously only available to high-end institutional investors accessible to everyone." Today, he is director emeritus of Financial Engines, an RIA with $88.2 billion in assets under management and about 430 employees.