Guests of honour are likely to include their two children Elwood Jack, three, and nine-month-old Willow Rose.
The exact details of the ceremony are being kept under wraps as the couple apparently want a private affair.
But according to reports in the Sun, the wedding will take place in November at a castle in Scotland.
The couple have reportedly sent out save-the-date invites, telling guests to meet at a pick-up point, where they will be taken to the mystery location. Not even Mark's bandmates Gary Barlow, Howard Donald and Jason Orange know where the party will be held.
Thirty-seven-year-old Mark proposed to Emma, an actress, in 2006, but they have never found the right time to seal the deal until now. With the band's Circus tour over, there is finally plenty of time to organise their dream nuptials.