January 1, 2008 all electronic submissions to the FDA must be in Electronic Common Technical Document (eCTD) format.
The eCTD delivery mechanism streamlines the submission process by insuring that only the most up-to-date documentation is submitted. FDA will still allow hard-copy paper submissions but after December 31, 2007 other electronic formats (such as eIND, eNDA or hybrid eCTD/eNDAs) will no longer be accepted. All regulated organizations intending to send submissions electronically are urged to contact the FDA prior to preparing submissions using the eCTD specifications. Start a dialogue with the FDA about your future eCTD submissions by sending an e-mail to email@example.com .
Read more about submissions and the eCTD format: