The Foreign Minister of Finland mr. Pekka Haavisto has just signed the letter requesting to join NATO. To my understanding mr. Jens Stoltenberg will receive it tomorrow.
here's the letter,
Your Excellency,
the President of the Republic of Finland has decided to confirm to the North Atlantic Treaty Organization Finland's interest to accede to the North Atlantic Treaty and in engaging in the accession talks with NATO. The Parliament of Finland was heard in the process.
I have therefore the honor to convey this interest to you on behalf of the Government of Finland.
I would also like to confirm that Finland’s decision to apply for NATO membership enjoys wide parliamentary and public support.
Yours sincerely,
Pekka Haavisto
Minister for Foreign Affairs
Finland
https://valtioneuvosto.fi/en/-/10616/finland-declares-its-interest-to-accede-to-nato