A postscript is an add-on to a letter that goes after the closing signature line. The common abbreviation to start a postscript line is "P.S." Using a postscript on a business leader has benefits and risks.
Postscript refers to script or writing presented after the main message of a letter. Having a P.S. line after your signature isolates that line from the rest of the letter's content. This isolation makes it easily visible to a reader. When you add a postscript line to a handwritten letter, it is also customary to add your initials after the line, according to The Emily Post Institute.
Postscript Pros and Cons
Adding a postscript to a business letter is a way to highlight or reinforce an important point, or to add an additional detail. The logic is that you can highlight a final major selling point or benefit in your correspondence by adding it to a separate line. For example, you might say, "P.S. Our solution is the only one recognized by XYZ Publication as a green solution in our industry."
An ineffective P.S. line projects the impression that you didn't organize your thoughts. If the postscript is a mere afterthought and not a compelling message, it makes more sense to work it into the body of the letter. Saying, "P.S. In case you didn't know, we do offer components for the Z81 model," sounds like a disconnected add-on.