When it comes to who should feel in charge of their own money, Beyonce said it best: "All the single ladies, now put your hands up."

Nearly all single women — 97 percent — said it's important to be engaged in managing their finances, according to a new Fidelity Investments study, "Single Women & Money."

However, three things are holding them back, the report found: underestimating their know-how, neglecting to plan for the future and saving too heavily in cash.

"Women are gaining a ton of financial power, but, they are too often in the back seat," said Alexandra Taussig, a senior vice president of women investors at Fidelity. Just 25 percent consider themselves primary decision-makers when it comes to family finances, according to a separate study from Fidelity.

Single women were less likely to consider themselves knowledgeable than other demographic groups on topics such as investing, retirement saving and creating a financial plan, Fidelity found.

"We have this lack of confidence," Taussig said.

Overall, 1 in 3 single women said they are concerned about their finances, compared with 1 in 5 single men.