You can add positive and negative buffers to your shipping rates by adding them at the carrier level or on specific service levels/shipping options (shipping costs), which alter the shipping amount displayed and charged at checkout.
You may add a positive buffer if you want to collect extra funds to cover costs associated with:
For reasons like those above, you may add a positive percentage or flat rate buffer such as the ones shown in the following examples:
You may add a negative buffer if you want to absorb some of the shipping costs yourself, lowering the cost to your customers. Here is an example:
For this [or another] reason, you may add a negative percentage or flat rate buffer such as the following:
There are 4 types of buffers that you can add to your account:
Account buffer - Adds a buffer to all service levels, for all carriers.
Carrier buffer - Adds a buffer to all service levels, for a specific carrier.
Service level buffer - Adds a buffer to a specific service level.
Duty/tax buffer - Adds a buffer to the duty and tax amount.