A method (250) for signaling a facsimile pass through mode over a voice over internet protocol voice service is disclosed. The method (250) includes: establishing (260) a voice over internet protocol call; detecting (270) that a facsimile tone has been received by a sender; and sending (280) a facsimile pass through notify message, from the sender, in response to detecting that the facsimile tone has been received. Advantageously, the method 250 can be adapted to inform the voice over internet protocol service provider about the details of an ongoing facsimile call in pass through mode. Advantageously, this can provide usage information, quality of transmission information, billing information and other useful information.