We were discussing the nature of bringing in Shabbat early. My question to my Rabbi which is still unanswered was whether or not someone who unknowlingly broke Shabbat (during the time when it was still when brought in early) would have had to bring a Korban in the days of the Temple or would the punishment be rabbinic in nature? Also, is being Yotzteh with an early Kiddush rabbinic or Deoritah (written or oral Torah directly derived)?

There is a question as to whether extending Shabbat is a Torah or rabbinic ordinance. In any case no sacrifice would be brought because the laws of punishment for the extension (Tosephet Shabbat) are not those of Shabbat itself.