Prince Harry will be warned that the crisis is far from over.
The governments of both the UK and Canada have been involved in discussions but the details of how to proceed could take weeks or even months to finalise.
Issues such as visas, tax payments, security and residency all need to be worked out.
Sources say Prince Harry and his wife Meghan have the end goal of moving to Los Angeles but will first settle in Canada and await for Donald Trump to no longer be president of the US.
The Queen, the Prince of Wales, Prince William, Duke of Cambridge, and Prince Harry, Duke of Sussex, will today meet for the first time since early November, when they last met at the Queen's Norfolk estate.
A lot has happened since then.
Prince Charles arrived in Sandringham last night, after a visit to Oman to offer the UK's condolences on the death of Sultan Qaboos bin Said.
Meghan will reportedly "dial in" via phone into the unprecedented summit today.
She is currently in Canada with her son Archie, who is now 8 months old.
Prince Harry is set to fly to Canada later this week. It is not known when he intends to return to the UK.
READ MORE:
• Megxit: Prince Philip's frustration - 'what the hell are they playing at?'
• From the Palace to The Crown? Fans speculate 'real reason' for Megxit
• Harry and Meghan: 'Megxit' won't move the needle on New Zealand republic debate, pundits say
• Editorial: Megxit royal drama ultimately just a sideshow for monarchy's future
"It is anticipated that at the end of the meeting a series of steps will be agreed, in line with Her Majesty's wish for this to be resolved within days not weeks," a royal source said, quoted by the Daily Mail.
"That's certainly the aim. But there will need to be an understanding that any decision will take time to be implemented and is complicated by issues including the HMRC (Her Majesty's Revenue and Customs), security and the like."
While no permanent solutions are expected that soon, next steps must be decided by the end of the day today (GMT time).