How to Implement GST and Indian Payment Methods in E-Commerce

Before configuring anything, map how your business actually transacts: primarily business-to-consumer or also business-to-business, mostly intrastate or genuinely interstate, and whether your turnover puts you within scope of mandatory e-invoicing. As of 2026, e-invoicing has been mandatory for GST-registered businesses whose aggregate annual turnover has crossed ₹5 crore in any year since 2017-18, a threshold in force since August 2023 (ClearTax, e-Invoicing under GST, verified 2026-09-08).

Product mix matters too — different categories can carry different GST rates and HSN codes, which affects what your catalogue and checkout need to calculate per line item rather than as one flat rate for the whole order.

Consider an online furniture store shipping across several states: it needs to correctly apply interstate tax treatment on most orders, handle a mix of GST rates across product categories such as raw wood pieces versus finished upholstered items, and decide — with its accountant — whether its turnover already requires e-invoicing or is approaching that threshold.

This is worth stating plainly: which GST rate applies to a product, how HSN codes should be classified, and whether your business is within scope of e-invoicing or specific reporting obligations are compliance decisions for your own chartered accountant or registered GST practitioner. This article describes what an e-commerce platform typically needs to configure — it isn't a determination of your business's tax position, and it shouldn't be treated as one.

The practical sequence is: your adviser confirms the applicable rules for your specific business and product range, and only then does the software get configured to encode those confirmed rules. Configuring tax settings from a generic online guide, without that confirmation, is a common and avoidable source of compliance risk.

Once your adviser has confirmed the applicable treatment, the platform work is mostly mapping: product tax classes tied to correct GST rates and HSN codes, invoices generated with GSTIN, HSN, and place-of-supply fields populated correctly, and — if your turnover crosses the confirmed e-invoicing threshold — invoices routed through the required e-invoicing process rather than generated independently.

On payment methods, UPI is close to a baseline expectation for Indian online shoppers alongside cards, netbanking and popular wallets, typically accepted through a licensed payment aggregator rather than integrated directly with each method. If the store offers any recurring or subscription payment, note that recurring transactions in India now run under the RBI's Digital Payments – E-mandate Framework, 2026, which requires additional authentication to register a mandate and applies additional authentication to most recurring debits above ₹15,000 per transaction, with a higher ₹1,00,000 threshold reserved for specific categories like insurance premiums and mutual fund payments rather than general subscriptions (Reserve Bank of India, Notification, verified 2026-09-08). Saved cards are handled through tokenisation rather than storing the actual card number, which is now the standard approach rather than an optional add-on.

A refund needs to reverse the tax calculation correctly and return the accurate net amount to the customer, not just the pre-tax product price. Rounding differences between the displayed order total and the sum of individual tax lines are a common, quietly annoying source of reconciliation mismatches if not tested deliberately.

Payment failure and timeout scenarios deserve specific testing too — what happens when a payment is deducted from the customer's account but the order isn't confirmed on your end. These edge cases generate a disproportionate share of support tickets and customer trust issues if they're only discovered after launch.

GST rates, e-invoicing thresholds and RBI payment rules have all changed at points through 2026, and there's no reason to expect that to stop. Treat tax and payment configuration as something reviewed on a schedule with your adviser and payment provider, not a one-time setup done at launch and left alone.

A short recurring check — quarterly is reasonable for most SMBs — of whether anything your platform assumes about tax or payment rules has changed is a small habit that avoids a much larger compliance scramble later.