The most common reasons you would see different rates in ShipStation are because:
There is a mismatch between shipment details in ShipStation and your carrier's web portal.
You have not enabled negotiated rates in ShipStation.
(UPS only) You have set a pickup type in ShipStation that's different than for your UPS account.
You may have entered different Ship To or Ship From addresses on the carrier portal than what is entered into ShipStation.
The package weight entered into ShipStation may be different than the package weight entered on the carrier site.
You must manually select the Residential Address option on both UPS.com to see the proper residential delivery rate.
*Note: the residential/commercial marker in ShipStation is determined by either the Stamps.com or Melissa address database, and may not reflect the same determination made by UPS.
Shipment details such as package weight, dimensions and package type are marked differently on the carrier's site than in ShipStation. UPS uses Dimensional Weight, so be sure you include the correct dimensions in both ShipStation and the carrier websites.
Order Confirmation is set to Delivery in ShipStation, which is an additional $2 fee, instead of the free Online Confirmation.
The negotiated rates option must be checked in the UPS setup window in
Settings > Shipping > Carriers & Fulfillment.
If you have not yet configured ShipStation to pull your negotiated rates from UPS, ShipStation will display the standard rates. Keep in mind that in this case, regardless of the rate displayed by ShipStation, UPS will invoice you the rate you have agreed upon.
Available Pickup Types in your UPS settings in ShipStation:
Daily Pickup: Must be enabled for UPS Negotiated Rates. Also, if you signed up for UPS through eBay's savings program, you get Daily Pickup rates.
Occasional Pickup: Gives you Retail Rates (more information provided on the UPS on-call pickup page).
Customer Counter: The rates you would receive at the UPS store counter.
Review the UPS Shipping Rates page for more details.
If you have checked the above settings and still believe you are being quoted at an incorrect rate in ShipStation, please review the Rate Discrepancies article in our Troubleshooting Help guide.
If you are still unable to identify the cause, please open a support case and include a screenshot of the full rate calculation on UPS.com or other carrier site, as well as the correlating order number in ShipStation for our team to investigate the issue.