The Duke and Duchess of Sussex must drop their "Sussex Royal" label after deciding to step down as working royals.
Following lengthy and complex talks, the Queen and senior officials are believed to have agreed it is no longer tenable for the couple to keep the word "royal" in their branding, the Daily Mail reports.
Harry and Meghan have spent tens of thousands of pounds on a new Sussex Royal website to complement their hugely popular Instagram feed.
They have also sought to register Sussex Royal as a global trademark for a range of items and activities, including clothing, stationery, books and teaching materials.
In addition, they have taken steps to set up a new charitable organisation: Sussex Royal, The Foundation of the Duke and Duchess of Sussex.
It has now been made clear that they will need to "re-brand", according to the Daily Mail.
The Mail understands that, amid what has been described as a "complex" situation, the "fine detail" is still being thrashed out.
However, it is understood the couple have accepted that, as part of their new working arrangements, they will not be able to use the Sussex Royal name as they had hoped.
The development is thought to represent a major blow to the Sussexes, who now face starting again and re-registering everything from their website to their charity under a new label.
Harry and Meghan first began using the Sussex Royal branding this time last year, after they split their household from that of the Duke and Duchess of Cambridge – known as Kensington Royal.
The Sussexes' Instagram page, @sussexroyal, has amassed 11.2million followers – the same number of fans as William and Kate's account.
It was a natural progression, therefore, for Harry and Meghan to use the moniker for their new charitable foundation, due to be launched this year with the support of Buckingham Palace.
And as they secretly prepared for a new life in Canada, it was clear that Sussex Royal was at the forefront of Harry and Meghan's plans.
Dozens of trademark applications were made for everything from bandanas to notebooks – although sources have always stressed that these were preventative measures to protect the trademark from others, and never intended for commercial use.
The couple also privately commissioned a new website. It went live last month to coincide with their bombshell announcement, with the introduction: "Welcome to the Sussex Royal community, your source for information on the Duke and Duchess of Sussex."
The couple's decision to step down as senior working royals and pursue 'financial independence' put a spanner in the Sussex Royal works.
It placed the Queen in an invidious position, given her long-held conviction of refusing to allow working members of the family to profit from their positions.
Announcing Her Majesty's decision to allow her grandson and his wife to pursue a new life abroad, officials made clear that the Sussex Royal title would still need to be re-evaluated.
All members of the family – including Harry and Meghan – were involved in the discussions, and it is understood they all agreed that, in light of the Sussexes' decision to step back, their use of the word "royal" would come into question.
Now, as well as giving up their HRH titles for work purposes and abandoning official appointments and patronages – including Harry's military roles – the Sussex Royal brand will have to be abandoned, according to the Daily Mail.
Such is the sensitivity around the issue, Buckingham Palace officials would not discuss the developments last night.
A source told the Mail: "In many ways this is inevitable given their decision to step down, but it must surely come as a blow to the couple as they have invested everything into the Sussex Royal brand The Queen would have had little choice, however."
"'The Sussexes' original plan – of being half-in, half-out working royals – was never going to work. Obviously, as the Queen has made clear, they are still much-loved members of her family.
"But if they aren't carrying out official duties and are now seeking other commercial opportunities, they simply cannot be allowed to market themselves as royals."
The couple are reported to have "no regrets" about their decision to step down.
Discussions about their charitable foundation took them to the prestigious Stanford University in California last week.
The foundation had been expected to launch in April, with the couple believed to be modelling the non-profit on those run by Barack and Michelle Obama, Bill and Hilary Clinton and Bill and Melinda Gates.
The Sussexes also recently appeared at a conference in Miami organised by banking giant JP Morgan.
They reportedly dined with Jennifer Lopez after flying in on the firm's private jet from Vancouver – despite previously calling for the world to embrace more eco-friendly ways to travel.
The appearance at the invitation-only summit is said to have earned the Sussexes up to US$1,577,326. Local media reported that Harry appeared on stage with his wife and Gayle King, a TV host who attended Meghan's baby shower last year.
A source told the New York Post that the Duke "opened up to the wealthy crowd about the childhood trauma of losing his mother", adding: "Harry also touched on Megxit, saying while it has been very difficult on him and Meghan, he does not regret their decision to step down as senior royals because he wants to protect his family.
"He does not want Meghan and their son Archie to go through what he did as a child."