Why 1 April 2026 Matters
The start of a financial year is always a reset point for GST, but 1 April 2026 carries more weight than usual. Several changes that were announced separately all take effect around the same date, and a few of them are not optional adjustments — they change what a valid invoice looks like and how input tax credit (ITC) is claimed. If your billing process is not ready, the first problems show up quietly: a rejected credit here, a late fee there, a buyer who refuses your invoice because the numbering looks wrong.
This is a practical checklist, written for a shop owner or small-business accountant, not a tax lawyer. Confirm specifics with your CA, but use this to make sure nothing slips through.
1. Start a Fresh Invoice Series
From 1 April 2026, you must begin a new invoice number series for the financial year. This is a long-standing GST requirement that many small businesses forget every year. The series must be unique for the financial year and should not continue last year's running numbers.
- Reset your invoice counter at the start of the year — for example
INV/2026-27/0001. - Keep the format consistent across all invoices for the year.
- Do not reuse or duplicate numbers; gaps and repeats both cause problems in an audit.
Good billing software does this for you automatically when the financial year rolls over, so you are not editing a counter by hand.
2. Prepare for the ITC Hard-Block on GSTR-3B
One of the biggest changes is that ITC values in GSTR-3B are becoming locked to what is auto-populated from your suppliers' filings, rather than freely editable. In plain terms: you can only claim the credit your suppliers have actually reported. If a supplier has not filed, or filed late, that credit will not be available to you in the same period.
What this means in practice:
- Reconcile your purchases against the auto-populated data every month, not at year-end.
- Chase suppliers who file late — their delay now directly blocks your cash flow.
- Keep clean purchase records so you can match invoice by invoice.
3. Know Whether the 30-Day IRN Rule Applies to You
Businesses above the e-invoicing threshold must upload invoices to the Invoice Registration Portal (IRP) and obtain an IRN within 30 days of the invoice date. Miss the window and the invoice cannot be reported, which means your buyer cannot claim ITC on it.
Check your turnover against the current e-invoice limit (Rs 5 crore). If you are close to or above it, build IRN generation into your billing flow so it happens at the moment of invoicing, not as a monthly catch-up task. We cover this in detail in our guide to the e-invoice limit in India 2026.
4. Apply the Correct GST 2.0 Rates by Invoice Date
The GST 2.0 rationalisation collapsed the old slabs into 0%, 5%, 18%, and 40%. Make sure every item in your catalogue is mapped to its current slab, and that your software applies the rate based on the invoice date, not the date you set up the product. The full breakdown is in our complete GST 2.0 slab list.
5. Watch for Auto Late Fees and Bank-Account Validation
Two quieter changes can catch you off guard:
- Automatic late fees are increasingly applied on delayed annual returns, so a missed deadline is no longer something you can quietly fix later.
- Bank-account validation on the GST portal can lead to auto-suspension if the registered bank details do not validate. Confirm your bank account on the portal is correct and active.
Your 1 April 2026 Checklist
- ☐ New invoice series configured for FY 2026-27
- ☐ Product catalogue mapped to correct GST 2.0 slabs
- ☐ Monthly purchase reconciliation routine in place for ITC
- ☐ IRN generation built into billing (if above the e-invoice limit)
- ☐ Registered bank account validated on the GST portal
- ☐ Return filing dates in the calendar to avoid auto late fees
- ☐ Billing software updated to the latest compliant version
Conclusion
None of these changes are hard on their own — the risk is that they arrive together and quietly break a billing process that worked fine last year. Software that handles the invoice series, applies rates by date, and generates IRNs at billing time removes most of the manual effort. InfiBis keeps GST current automatically so the 1 April reset is one less thing on your plate. For the rate details, see our GST 2.0 slab list, and confirm the specifics with your accountant.