April 1, 2026 wasn’t just the start of a new financial year. It was the day a wave of new GST rules quietly took effect — changing how businesses issue invoices, claim input tax credit, manage their compliance calendar, and interact with the GST portal.

If you didn’t catch every change, you’re not alone. The CBIC rolled these out through multiple notifications, circulars and rule amendments over several weeks, which makes it almost impossible for a busy business owner to track everything in one place. So we’ve gone through every notification, amendment and advisory to bring you a single breakdown — not just what changed, but what you need to do about each change. Whether you run a trading business in Mumbai, a SaaS company in Pune, or a manufacturing unit in Ahmedabad, these are the compliance actions you cannot afford to skip.

01GST e-Invoicing 2026: mandatory for far more businesses

The biggest headline is the expansion of mandatory e-invoicing. Since its phased introduction in 2020, the turnover threshold has been steadily lowered. From 1 April 2026, e-invoicing is mandatory for every registered business with aggregate turnover above ₹5 crore in any financial year from 2017-18 onwards — a significant drop that brings lakhs of additional businesses under the mandate.

₹10cr+

Earlier threshold

→

₹5cr

From April 2026

What this means for your business

If your business has crossed ₹5 crore in any year since GST began, you must now generate an Invoice Reference Number (IRN) for every B2B invoice through the Invoice Registration Portal (IRP). Every B2B invoice, credit note and debit note must carry a valid IRN and QR code. An invoice issued without an IRN is not a valid tax invoice — which means your buyer cannot claim ITC on it.

02GST ITC Rules 2026: tighter controls on Input Tax Credit

The second major area of change is Input Tax Credit. The government has tightened ITC steadily over recent years, and 2026 takes it further. The core change: ITC is now almost entirely governed by what appears in your GSTR-2B. If an invoice doesn’t appear in your auto-populated GSTR-2B, you cannot claim ITC on it — even if you hold a valid tax invoice.

The GSTR-2B matching problem

The system-generated GSTR-2B is now the single source of truth for ITC eligibility. So if your supplier files their GSTR-1 late, files it with errors, or doesn’t file at all, your credit gets stuck. The rules now make it explicit that no provisional ITC can be claimed outside GSTR-2B — the earlier practice of claiming credit on a self-declaration basis for mismatched invoices is formally closed.

For businesses, this creates a direct operational challenge: your compliance is only as good as your suppliers’ compliance. If a supplier fails to report your invoice in their GSTR-1, you lose the credit — which effectively forces you to monitor your entire supply chain’s filing behaviour.

03Invoice Management System (IMS): what changed in April 2026

The IMS is the portal feature where recipients can accept, reject or keep invoices pending before they flow into GSTR-2B. Previously it was limited in functionality and rarely used. The April 2026 update changes that.

Key IMS changes

• Mandatory action on mismatched invoices. Invoices with value discrepancies above a threshold now require explicit acceptance or rejection on the IMS before they auto-populate into GSTR-2B. Earlier, all supplier-reported invoices appeared automatically; now, flagged invoices need manual intervention.
• Credit note management. The IMS now lets recipients track and accept or reject credit notes issued by suppliers — critical for businesses with frequent returns, discounts or post-sale adjustments. A credit note not accepted on the IMS may not reflect correctly in your ITC computation.
• Deemed acceptance timeline. Invoices not acted upon within a specified period are now deemed accepted. Inaction has consequences — you cannot ignore the IMS any longer.

04A fresh invoice series from 1 April 2026

One of the simpler but most-overlooked changes is the requirement to start a fresh invoice series from 1 April each year. Many businesses already do this by practice, but the rules now formalise it — with specific consequences for non-compliance. The invoice serial number must be unique and sequential within a financial year. Carrying a series forward without resetting can create duplicate invoice numbers when matched across years, causing problems in GSTR-1 filing and e-invoicing validation.

05LUT renewal for FY 2026-27: exporters must act now

If your business exports goods or services without payment of GST under a Letter of Undertaking (LUT), you must renew it every financial year. It’s a routine requirement that businesses frequently forget — and the consequence is painful. Without a valid LUT for FY 2026-27, you must pay IGST on all export invoices and then claim a refund later, and that refund can take months.

06IMS credit-note obligations: a new compliance layer

The rules introduce specific obligations around credit notes through the IMS. When a supplier issues a credit note — for returns, rate differences or damaged goods — the recipient must now actively accept or reject it on the IMS for it to correctly reduce the supplier’s tax liability. Credit notes used to flow automatically; now, an unaccepted credit note creates a mismatch between the supplier’s GSTR-1 and the recipient’s GSTR-2B, triggering potential notices and reconciliation work. For high-return businesses — retail, FMCG, e-commerce — this needs systematic handling.

07QRMP selection closed 30 April: did you pick the right frequency?

Under the Quarterly Return Monthly Payment (QRMP) scheme, eligible businesses can file GSTR-1 and GSTR-3B quarterly instead of monthly. The selection window for FY 2026-27 was open until 30 April 2026; if you didn’t make a selection, the system carries forward last year’s frequency.

Businesses with turnover up to ₹5 crore can opt for QRMP, cutting returns from 24 to 8 a year. The trade-off: your customers only see your invoices in their GSTR-2B after you file your quarterly GSTR-1, which delays their ITC claims. That can create friction with larger customers who need real-time credit visibility, so weigh whether QRMP suits your model or whether monthly filing gives customers a smoother experience.

08Complete compliance checklist: new GST rules 2026

09Frequently asked questions

10The bottom line

The new GST rules 2026 aren’t cosmetic tweaks. They represent a fundamental tightening of the compliance framework — from how you issue invoices, to how you claim credit, to how you manage your invoice data. Businesses that adapt quickly will stay out of trouble. Those that ignore the changes will face notices, blocked ITC and unnecessary penalties. The rules have changed; your compliance should too.