When you set up account codes on the system, users at extensions set to Forced Account Code Entry must enter an account code before they can dial outside calls. Other extensions can also use account codes but on a voluntary basis. They can enter

When an account code is entered during a call, the caller on the other end does not hear the touch-tone digits dialed. 

If SMDR is used, the account code assigned to a call is included in the SMDR record for that call. 

You can program the Account Code Entry button on a phone. Use a button with LEDs/LCD. 

For faster entry of frequently used account codes, you can program an account code on an Auto Dial button or as a system speed dial or personal speed dial number (but not as a marked system speed dial number).