@Kyle_M It's possible that requiring customers to check a box agreeing to your shipping and returns policy could lead to some customers abandoning the checkout process. However, it's also possible that it could have the opposite effect and lead to fewer returns and customer service issues related to shipping.
It's difficult to say for sure without testing it on your site, but one way to minimize the risk of customers abandoning the checkout process is to make sure the checkbox is clearly labeled and the link to your shipping and returns policy is easily accessible. You can also consider explaining the benefits of agreeing to the terms, such as ensuring the customer is aware of the shipping process, and how it will help them in case they need to return the product.
It is also recommended to make it clear that this checkbox is optional, as some people may feel that they are being forced to accept the terms and may leave the website.
Ultimately, it's important to weigh the potential downsides against the potential benefits and test the change on a small scale before rolling it out site-wide.