Where to find it
Settings > Returns > Shipping, under Return Shipping Settings.
[Screenshot: Shipping tab — Preferred returns carrier dropdown]
What this is
Lowest cost — Onward compares available rates and picks the cheapest. This is the default behavior.
A specific carrier — Onward uses this carrier whenever rates are available from it.
Preferred returns carrier works in conjunction with Return label provider, as the label provider determines what carrier rates are available. Carrier accounts are added through ShipSidekick, not in Onward.
If no rates are available from your preferred carrier, Onward falls back to the lowest-rate label so the return isn't blocked.
Choosing a carrier
A specific carrier is useful when you have negotiated rates worth consolidating volume into, when your warehouse receiving process is built around one carrier's scans, or when one carrier's drop-off coverage is better in your customers' area. Otherwise Lowest cost works for most stores.
Exceptions can route specific returns to a different carrier — for example, oversized or heavy items, or a specific region. See Using Exceptions in Returns Settings.
Related settings
Return label provider — this setting only applies when labels are automatic
Products requiring Hazmat Labels — may constrain which carriers can be used