The Dawat-E-Walima will take place on October 18, the notification leaked by pinkvilla.com states.
The card, sent on behalf of Khan's mother Sharmila Tagore and bearing the Pataudi crest, says: "I am delighted to inform you that we are having a Dawat-E-Wamila to celebrate the wedding of Saif and Kareena on Thursday 18th October 2012.
"While the formal invitation will reach you in due course, this advanced notification will enable you to block this wedding date in your diary.
"Saba, Soha and I along with other members of our family look forward to welcoming you on this joyous occasion. With warm regards, Begum Mansoor Ali Khan."
Talking about her marriage plans, the Heroine star recently said: "Post-marriage I will be Kareena Kapoor Khan. That means I have the privilege of having two of the most powerful surnames in Bollywood attached to my name."
The couple's wedding has been repeatedly postponed due to their respective filming commitments.
Watch the video for 'Saaiyaan' from Kapoor's Heroine below: