The consent required to record a phone call is a matter of state law. Some states are called "one-party consent states" because either party to a phone call can record without notice to the other. Wiretapping is the recording of a phone conversation by a third party, who is not a party to the conversation and is generally illegal without a court order. California is not a one-party consent state according to the wiki on the subject.
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If you inform them (before you hit RECORD) that you intend to record the call, and ask for their consent, then it MAY be legal. If you don't, as others have stated, it is a matter of state law -- some states allow "one party recording," some (most, I believe) do not. CA does not allow "one party recording." It also gets thorny if it is an interstate call, as that would involve federal law, which generally frowns on "one party recording." SHort story -- don't record. If you feel you must, get the other party's consent BEFORE you record, and then have them repeat that consent as part of the recording. "I am recording this call, you have indicated that you consent to the recording of this call, is that correct?"
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If you need to have a conversation with a company and they won't allow you to record the call, the answer is to have the conversation in writing. Yes, it will slow things down, but there won't be any doubts about what was "said."
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