© Stuart Nicol / The Scottish Government / AFPScotland's First Minister Nicola Sturgeon working on her Section 30 letter to the British Prime Minister Theresa May, Edinburgh on March 30, 2017.
Scottish First Minister Nicola Sturgeon signed the Section 30 letter requesting transfer of powers to Holyrood on Friday morning.
May's government has already said it will decline the request, however.
"As you are aware, the Scottish Parliament has now determined by a clear majority that there should be an independence referendum," Sturgeon wrote.
"The purpose of such a referendum is to give people in Scotland the choice of following the UK out of the EU and single market on the terms you negotiate, or becoming an independent country, able to chart our own course and build a genuine partnership of equals with the other nations of the UK.
"I am therefore writing to begin early discussions between our governments to agree an Order under section 30 of the Scotland Act 1998 that would enable a referendum to be legislated for by the Scottish Parliament."
On Tuesday Scottish MSPs voted 69 to 59 in favor of requesting another referendum, which would be held sometime between autumn 2018 and spring 2019.
A spokeswoman for May said: "The prime minister has been clear that now is not the time for a second independence referendum, and we will not be entering into negotiations on the Scottish government's proposal.
"It would be unfair to the people of Scotland to ask them to make a crucial decision without the necessary information about our future relationship with Europe, or what an independent Scotland would look like.
"We have been joined together as one country for more than 300 years. We've worked together, we've prospered together, we've fought wars together, and we have a bright future. At this crucial time we should be working together, not pulling apart."
Comment: What is unfair to the people of Scotland is denying them their right to self-determination.