The following information was extracted from the IRS Publication 1437 dated December 2012:
IRS acknowledges each transmission of electronic return data.
A return can be acknowledged (ACK) as accepted, even though it has not been through any mathematical verification. There are two types of ACK files: the Transmission ACK File and the Validation ACK File. The IRS will provide an outbound mailbox for pick up of ACK files by the transmitter.
The Transmission ACK File is generated if there is a problem in the basic formatting of the entire file. If a Transmission ACK File is generated, individual forms and schedules are not validated. This ACK file should be available within two workdays after receipt of a transmitted file.
The Validation ACK File is generated when there is a problem within the return. The ACK file counts for the number of
1041 Forms, related forms and schedules. The file provides the reject code numbers for up to 96 errors per return.
January 28, 2013 is the date to begin transmitting live 1041 e-file returns for Tax Year 2012.