Special with price 0

If you have defined a special with price 0 (accidentally), you don't see that price in the catalog but if you put that item in the cart, you see price 0.

See this post: viewtopic.php?f=201&t=210762#p750355 . Specials do apply on products directly but free checkout also applies with Opencart. However, the free checkout module is a payment extension option which is applied via customers activities and allowed by store owners, not from the products page specifically unless using an extension.