A study sponsored by Fidelity Investments conducted in April tracked partners’ confidence in handling financial tasks when they were more involved and less involved — finding that couples who worked together had greater confidence about their financial future.

The company surveyed 1,662 couples across the country, with an average age of 52, who were either married or in a long-term committed relationship and living together. The respondents had either an annual household income of $75,000 or a minimum of $100,000 in assets to invest. When they were asked about their ability to assume full responsibility for their retirement finances and strategy, almost all — 93 percent of those who said they had primary responsibility and 87 percent with joint responsibility, said they felt confident in doing so.

By contrast, only 52 percent of the less involved partners expressed confidence in taking over the financial role. Notably, those who were not participating showed more unease when asked about “not being prepared financially if my significant other passes away first,” with 41 percent of the less involved respondents saying they were concerned, versus only 10 percent of those who said they had primary financial responsibility and 18 percent who said they handled tasks jointly.

Even a well-intentioned spouse can leave a partner feeling uncertain about her ability to make good choices alone — but worried and fearful at worst, especially if one is left in potential financial jeopardy.

Kathleen M. Rehl is a financial adviser and researcher in St. Petersburg, Fla., and the author of “Moving Forward on Your Own: A Financial Guidebook for Widows.” She recalled a newly widowed client who had gladly ceded the financial decision-making to her husband for years. The client was following a gut instinct in hiring her, Ms. Rehl said, and expressed it this way: “I never really understood that stuff that Jim did, but my tummy tells me it might be wrong.”

When Ms. Rehl looked at her client’s portfolio, she found 90 percent of the holdings were in international stocks — an aggressive risk profile for any investor, let alone a retiree in her 70s. Together, they developed a more balanced portfolio, composed of a blend of stock and bond index funds designed to weather market volatility. Even when they agreed to rejigger the investments, it proved hard for Ms. Rehl’s client to make such a big decision alone, even though she eventually followed through. “She said, ‘Stop, I can’t do it,’” Ms. Rehl said. “She said, ‘It’s like I’m slapping Jim in the face.’”

Facing major choices alone can be disorienting — even when a couple have prepared for it together.

When Liz Hobert, of Mount Dora, Fla., 68, and her husband, Bruce, were in their 50s, they wanted to make sure they both had a clear view of their finances — so they enrolled in a financial course held at a local community college.