When Terry Kass received an email from PayPal in late December encouraging her to donate to charities through its Giving Fund platform, she searched its website for ones she could help. She settled on 13 groups — most in her Chicago suburb — and gave a total of $3,700 to them.

But when Ms. Kass followed up with one of the recipients, the Highland Park-Highwood Legal Aid Clinic, she discovered that the group had not been notified about her gift, nor had even received it. It was not a fluke, she said. She learned that 10 of the 13 groups — all of which had profile pages on the PayPal site that included biographical information and mission statements — were also unaware of donations through the site, she said.

A federal class action lawsuit filed on Tuesday said that Ms. Kass and thousands of other donors have been misled by PayPal Giving Fund, and that their gifts never reached the intended charities. The company has a policy of redirecting contributions to other organizations if the intended charity does not register an account with the site, Ms. Kass said, adding that neither donors nor intended charities are informed of any switch.

“I don’t want to file my taxes to the federal government saying I gave to a charity that never got my money,” Ms. Kass, a retired lawyer, said in an interview. “It’s their money. They are entitled to the money.”