Thirty-eight states and the District of Columbia permit individuals to record conversations to which they are a party without informing the other parties that they are doing so. These laws are referred to as one-party consent statutes, and as long as you are a party to the conversation, it is legal for you to record it.
Twelve states require, under most circumstances, the consent of all parties to a conversation. Those jurisdictions are California, Connecticut, Florida, Illinois, Maryland, Massachusetts, Michigan, Montana, Nevada, New Hampshire, Pennsylvania and Washington. Be aware that you will sometimes hear these referred to inaccurately as two-party consent laws. If there are more than two people involved in the conversation, all must consent to the taping.