I need to turn off express store, but NOT delete or remove it altogether. How is this done please? using expression engine 2.6
If you only need to remove it from the front end of the site I recommend just deleting all your store-related templates (eg all cart and checkout templates) and removing any "add to cart" template code from your product template(s). If you aren't using version control for your templates then make a backup first, obviously.
For good measure you could also disable all payment methods in Store's settings.