Customers of four top fund firms — Fidelity Investments, Charles Schwab Corp., TD Ameritrade Holding Corp. and Wells Fargo & Co. — faced technical glitches today that prevented them from accessing some account information.

Clients were primarily affected in the morning after the the open of U.S. markets. Each of the companies said the issues had been resolved.

Unable to perform a variety of tasks from making trades to viewing account balances, customers took to Twitter to rail. The outages occurred as mutual fund and brokerage firms enter a busy period when investors grapple with year-end tax and financial matters. That process is unusually fraught this year due to the pending tax legislation in Congress. It’s unclear if the issues at the four companies are related.

In a posting on its Twitter page this morning, Fidelity reported “issues with our website” and said it was looking into the matter. The company didn’t disclose the precise nature of the problem. About 30 mintues later, Fidelity said the matter had been cleared up.

It was the second time in two weeks Fidelity customers were impacted by website glitches. On Nov. 29, the company reported a technical error that blocked clients from online brokerage accounts. The issue was resolved the same day.

This morning Schwab said: “This morning, some clients experienced issues accessing their account balances online due to an internal technical issue,” according to a statement from Mayura Hooper, a spokeswoman for the company. “Trading was not impacted. The issue was quickly resolved and online functionality has been restored.”

Several TD Ameritrade customers posted Tweets in the morning saying the company’s app was frozen and that the problem had cost them money. Others said they couldn’t get through by phone either. The posts prompted the company to respond online to those who complained but TD Ameritrade didn’t fully acknowledge the nature of the problem fast enough.

“We had an issue where clients were experiencing some slowness on our trading site and mobile apps for about 15 minutes this morning,” Kim Hillyer, a spokeswoman with TD Ameritrade, said by email. “The issue has since been resolved.”

Wells Fargo spokeswoman Emily Acquisto said an internal issue caused some clients to experience issues accessing their Wells Fargo Advisors accounts online early this morning for roughly an hour.

“Wells Fargo Advisors worked quickly to resolve the issue, and access is now restored,” she said in an emailed statement.