In your Shift4Shop Online Store Manager, you will find a series of Shipping Settings that can be found by going to Settings > Shipping and then clicking on the Enter Settings button under the "Carrier Settings" section.
Once there, click on the + Icon next to "Shipping Settings to reveal a series of checkboxes. Within this area, you will see a checkbox titled "Exclude free shipping items from real time calculation."
The purpose of this setting is to account for situations where orders might have items that are eligible for your store's automatic Free Shipping function*, as well as additional items that are not eligible to be shipped for free.
*The automatic free shipping function itself comes into play when your shopper orders an individual item that is marked for free shipping (under the product's Information Tab) or otherwise if their entire order meets eligibility for a Free Shipping promotion via the store's Promotion Manager.
With this setting enabled, the real-time shipping calculation service will remove the free shipping item(s) from the shipping calculation requests and return a rate based on the other products.
Real Time Calculation
When you integrate your Shift4Shop store with a specific shipping carrier like USPS, your store will be able to connect to the carrier and calculate a relatively accurate shipping cost for your shoppers and their orders.
To explain how it works; when an order is placed, the store takes into account where the order will be shipped from (you or your drop shipper's location), where the order is going to (your shopper's address) and how much the order will weigh (all item weights summed). Shift4Shop's software then sends this information to the respective shipping carriers and requests a quote of the shipping rates for the order. Once the rates are received, they are added to the order's selection areas and your shopper can select which method they'd like to have their shipment sent through. We refer to this as a real time shipping calculation.
By enabling the "Exclude free shipping items from real time calculation" checkbox, the store will submit the collective weight of the order for the additional items but remove the free shipping item(s) from the shipping request to return rates for the non-free shipping items alone.