Extra Space on Right Side

Hi all. I have some mystery extra space on the right side of my site. The content is centered, but when the browser window is opened beyond the width of the content there’s a horizontal scroll bar at the bottom- meaning something is widening my site an extra 170 pixels or so.

This is the site: https://www.fortaxreasons.com/

I can’t tell what’s causing it. I’ve gone through my CSS style sheet and everything appears to be set to width of the header- 900 pixels. The strange thing is, I copied the style sheet and most of the other .php files from my other site which does not have this problem:

https://www.benlevin.net/

Anyone experience this problem before? I’ve seen several post on the forums but never with any post resolving the problem. Thanks so much, I know this is a very rudimentary problem.