An Order Management System (OMS) is the central order-of-record across multiple sales channels. For a brand selling on Shopify + Amazon + Flipkart + Myntra + Nykaa, the OMS unifies order intake, inventory allocation, fulfilment routing, returns, and refund handling.
Common choices in 2026: Linnworks, ShipStation, Shipworks (UK + US-led), Unicommerce + Vinculum (India-led, deep marketplace connectors), Increff (India warehousing focus), or custom (when channel mix or workflow exceeds what off-the-shelf supports).
The architecture decision: OMS sits between the storefront / marketplace + the WMS / 3PL + the accounting system. Inventory allocation across channels (Shopify-DTC + FBA + Flipkart-FSF + Myntra-fulfilment) is the most consequential OMS configuration -- mis-allocation either overpromises sub-channel stock or strands inventory in low-velocity channels.