Summary: This content is an article/explainer highlighting five common compliance mistakes businesses are making after the GST rate changes effective from 22 September 2025. It states that the 12% GST slab has been removed, with products and services shifting mainly to 5% or 18%, and advises businesses to map HSN codes to the revised rates using the CBIC tariff notification. It explains that a reduction in GST rate does not require ITC reversal unless the supply becomes nil-rated, and emphasises verifying the product classification before reversing credit. The article notes that goods purchased or manufactured before 22 September 2025 but supplied later must be invoiced at the new GST rate based on the date of supply, requiring businesses to track transition stock. It also discusses the introduction of the 40% GST rate in place of the earlier 28% plus cess structure for specified categories and advises affected businesses to recalculate effective tax rates. Further, it states that with the Invoice Management System becoming mandatory from April 2026, businesses should verify supplier invoices for correct GST rates before claiming ITC. It recommends checking product classifications against the CBIC notification, updating billing systems, and correcting returns through GSTR-1A amendments where available.
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Mistake 1: Still Using the 12% Rate on Invoices
The 12% slab no longer exists. Every product or service that sat at 12% has moved — most went down to 5%, some went up to 18%. Businesses still invoicing at 12% after 22 September 2025 are either overcharging customers or underreporting their tax liability. Both create problems. Overcharging means the buyer claims incorrect ITC. Underreporting means a demand notice with interest.
The fix is simple but must be done at the HSN code level, not just by changing a rate in the settings. Map every product or service to its new rate using the CBIC tariff notification — not a summary article, not a third-party guide, the actual notification at cbic.gov.in.
Mistake 2: Assuming the Rate Reduction Means ITC Reversal
We’ve seen businesses unnecessarily reverse ITC on inputs after their output rate dropped from 18% to 5%. This is wrong. ITC reversal is required when supplies become exempt — nil-rated — not when the rate merely reduces. If your product remains taxable at the new 5%, all previously availed ITC on your inputs stays valid. Don’t reverse credit you’re entitled to keep.
The exception: if your specific product moved to nil-rated (0%), ITC on related inputs does need reversal. Verify your exact product’s new classification before touching your ITC.
Mistake 3: Not Updating Transition Stock
Goods manufactured or purchased before 22 September 2025 but sold after that date have a different tax treatment. The GST rate applicable is determined by the date of supply, not the date of manufacture or purchase. Stock sitting in a warehouse on 21 September 2025 must be invoiced at the new rate when it’s eventually sold — even if it was produced under the old rate structure.
This creates an accounting mismatch businesses aren’t anticipating. The input tax was paid at the old rate. The output tax is now at the new rate. In some cases this creates an ITC accumulation. In others it reduces margins. Neither outcome is visible without specifically tracking your transition stock position.
Mistake 4: Ignoring the 40% Category Entirely
The new 40% rate replaced the old 28% + cess structure for luxury and sin goods. Many businesses dealing in adjacent categories — premium vehicles, aerated beverages, online gaming — have moved into or near this new rate without fully appreciating the cost impact.
The compensation cess is simultaneously being phased out for most categories, which changes the overall calculation. Businesses in affected sectors need to recalculate effective tax rates, not assume the old combined figure simply transfers to the new structure.
Mistake 5: Not Checking Whether Suppliers Updated Their Rates
With the Invoice Management System now mandatory from April 2026, every invoice your supplier sends lands in your IMS dashboard before it hits GSTR-2B. If your supplier is still invoicing at 12% on a product that moved to 5%, you’re claiming ITC at 12% on a supply that should have attracted 5% — a discrepancy the department’s system will catch.
The responsibility to claim correct ITC sits with you, not your supplier. Review IMS invoices for rate accuracy, not just for whether the invoice exists.
What to Do Now
If any of these five situations apply to your business, the action is the same in every case: verify your specific product or service category against the CBIC notification, correct your billing system, and fix any return periods where the wrong rate was applied through GSTR-1A amendments where still available.
Businesses that address these issues now, before the first GSTR-9 filing under the new structure, will have a significantly cleaner annual return than those who discover them in December.
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