After the signature.
the signature of a letter is called the complimentary close or ending
I would not recommend a typed signature on any letter unless you are sending it electronically. In all cases, a physical letter should have the actual signature of the sender. The recipient of a letter of recommendation that has a typed 'signature' will not hold the recommendation in high regard. A photocopy of a signed letter is preferable to a typed signature.
It is part of the business letter that authenticates statements and shows the signature of the letter sender.
If you are asking about your signature (as when you sign a letter), no period is needed. At the end of the letter, you sign your name in your own handwriting; and in a typical business letter, you will also type your name below your signature so that people who might not be able to read your signature will know what your name is. But in neither case is a period necessary. For example,Sincerely yours,[my handwritten signature would go here here]Donna L. Halper [
Signature
A request for a signature verification can be done in a letter. Ask the person to verify they did or did not sign the document in question and state the date of signature.
After your signature.
It is a signature which is readable and takes a complete form of letter strokes.
Yes, the signature is one of the main (essential) parts of a business letter.
signature
An addendum is very similar to a P.S. in a letter. While a P.S. goes after the signature however, an addendum comes before the signature.