It said earlier on its website: "We are currently experiencing some system issues that may impact the accuracy of balances and positions in your account, as well as your ability to place trades."
The issue was later fixed, according to online traders and the firm, which issued the following statement: "Earlier this morning, we encountered an issue on the main www.tdameritrade.com website and some mobile channels that briefly impacted clients' ability to log in or place trades, resulting in a poor experience. During this time, clients could access their accounts and place trades through the thinkorswim platform and the thinkorswim mobile app."
Some investors, though, also said they were having problems with Thinkorswim in the morning.
"The issue was quickly resolved and client trades are being executed as usual," TD Ameritrade said. "Outages of any kind are not acceptable to us, and we're working with impacted clients to address any lingering issues or concerns they may have. We apologize for the inconvenience and take the performance and reliability of our trading platforms very seriously,"
TD Ameritrade's trading problems came the same day as rival Vanguard said it was dropping commissions on stocks and options. This development was announced about three months after Charles Schwab made the first such move, paving the way for it to say in late November that it planned to purchase TD Ameritrade for $26 billion.