Amazon, Flipkart and Myntra penalise sellers for late dispatch, late delivery, cancellation and quality issues — typically ₹50–₹500 per breach plus listing demotion or account suspension after threshold breaches. The fastest-payback fix is moving to a 3PL with marketplace-cut-off-aware dispatch and SLA dashboards: most sellers see SLA-related penalties drop 70–90% within 60 days.