How to begin and end letters is very important. In a formal letter.

When you begin your letter with Dear Sir(s) or Dear Sir or Madam, end your letter with Yours faithfully.

When you begin your letter with Dear (Fyodor) or Dear Mr/Mrs/Ms (Yurchikhin), end your letter with Yours sincerely.

If you know the person you are writing a letter very well, you might begin with Dear (John/Maria) and end with either Yours or Best wishes.