In India’s GST system, output tax is the tax you charge customers on your sales, and input tax is the GST you pay to your own suppliers on business purchases. Your liability for each filing period is the difference: total output tax minus the eligible input tax credit (ITC) you can claim. That subtraction is the whole point of the design, because it ensures each business in the chain pays tax only on the value it adds rather than on the full price of what it sells.
Output Tax: What You Collect on Sales
Section 2(82) of the CGST Act defines output tax as the tax chargeable on taxable supplies made by you or your agent, excluding tax you owe under the reverse charge mechanism.1Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 2 When you issue a sales invoice with GST on it, the tax figure on that invoice is your output tax.
The charge itself comes from Section 9 of the CGST Act, which levies central GST on intra-state supplies at government-notified rates up to a statutory cap of twenty percent.2Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 9 For inter-state supplies, Section 5 of the IGST Act applies, with a cap of forty percent.3Central Board of Indirect Taxes and Customs. The Integrated Goods and Services Tax Bill 2017 Actual notified rates for most goods and services fall into five slabs: zero, five, twelve, eighteen, and twenty-eight percent.4Development Commissioner for Micro, Small and Medium Enterprises. Rate of GST on Services
Getting the rate right matters. Classifying a supply under the wrong slab either short-collects tax, which creates a liability with interest, or over-collects, which can complicate refunds for your buyer. The sum of tax across all your sales invoices for the period is your gross output liability before any credits.
Input Tax: What You Pay on Purchases
Input tax is the mirror image. Section 2(62) of the CGST Act treats it as the central tax, state tax, integrated tax, or union territory tax charged on any supply made to a registered person. It covers raw materials, capital goods, professional services, imports, and other business inputs. It also includes GST you pay under reverse charge, where the payment obligation shifts from the seller to you as the buyer.
A purchase invoice from a GST-registered supplier should show the tax separately, split into CGST and SGST for intra-state buys or IGST for inter-state buys. Those amounts feed the pool of credits you can potentially set off against your output tax.
How the Offset Works
Add up the output tax you collected during the period, subtract the eligible input tax you paid, and the result is what you owe. If you collected ₹5,00,000 in output tax and paid ₹3,20,000 in input tax, you owe ₹1,80,000.
When input tax exceeds output tax, the excess carries forward against future liability. Exporters and businesses making zero-rated supplies can claim a refund of accumulated ITC under Section 16 of the IGST Act, either by supplying without payment of tax under a bond or letter of undertaking, or by paying IGST and claiming it back.5Central Board of Indirect Taxes and Customs. Integrated Goods and Services Tax Act – Section 16 Zero Rated Supply
The Set-Off Order You Have to Follow
Credits cannot be applied at random. Section 49 of the CGST Act sets a specific sequence, and IGST credit must be exhausted before CGST or SGST balances are touched.6Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 49
- IGST credit is set off first against IGST liability, then against CGST and SGST liability in any proportion.
- CGST credit is set off first against CGST liability, then against IGST liability. It cannot be applied to SGST.
- SGST credit is set off first against SGST liability, then against IGST liability. It cannot be applied to CGST.
The cross-restriction between CGST and SGST is where many businesses slip up. CGST credit will never reduce a state tax bill, and SGST credit will never reduce a central tax bill. Only IGST credit flows freely across both.6Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 49
Conditions for Claiming Input Tax Credit
Eligibility is not automatic. Section 16(2) of the CGST Act lists conditions that must all be met before ITC can be claimed:7Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 16
- You hold a valid tax invoice or debit note from a registered supplier.
- The supplier has reported the invoice in their GSTR-1, and it appears in your GSTR-2B without restriction.
- You have received the goods or services. For goods delivered in instalments, credit is available only after the last instalment arrives.
- The tax on the supply has actually been deposited with the government by the supplier, whether in cash or through their own ITC.
- You have filed your return under Section 39 for the relevant period.
A payment discipline rule catches many businesses off guard. If you fail to pay your supplier the invoice amount, including the tax, within 180 days of the invoice date, you must reverse the ITC claimed on that purchase along with interest.7Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 16 Once payment is made, the credit can be reclaimed, but the cash-flow effect in between can be significant.
Blocked Credits Under Section 17(5)
Some purchases can meet every eligibility condition and still be blocked from ITC entirely. Section 17(5) of the CGST Act lists them.8Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 17 The major categories:
- Motor vehicles seating thirteen or fewer, unless used for resale, passenger transport, or driving instruction.
- Food, beverages, and outdoor catering, unless you supply the same items or they form part of a taxable composite or mixed supply.
- Club and fitness centre memberships, regardless of business purpose.
- Beauty treatment, cosmetic surgery, and health services, unless you supply the same category.
- Works contract services and goods used for construction of immovable property on your own account, except for plant and machinery.
- Employee travel benefits on vacation, unless required by another law.
- Goods lost, stolen, destroyed, or given away as free samples.
The construction block generates the most disputes. Attempts to claim ITC on office renovations or warehouse construction get denied. The plant-and-machinery exception is narrow and does not extend to buildings or civil structures, even if those structures house manufacturing equipment.8Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 17
The Deadline for Claiming ITC
Old invoices cannot be accumulated indefinitely. Section 16(4) of the CGST Act sets a hard cutoff: ITC on any invoice must be claimed by the thirtieth of November following the end of the financial year the invoice belongs to, or the date you file your annual return for that year, whichever is earlier.7Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 16 Miss that window and the credit is gone permanently.
Reverse Charge Changes the Cash Timing
Under the reverse charge mechanism, the buyer pays GST directly to the government instead of the seller collecting it. It applies to categories notified under Section 9(3) of the CGST Act, and to registered businesses buying from unregistered suppliers under Section 9(4).2Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 9
The rule that trips up buyers: reverse charge tax must be paid in cash through the electronic cash ledger. You cannot use an existing ITC balance to discharge the reverse charge liability. Once paid, the tax becomes fully eligible for ITC in your next return, provided the goods or services are used for business purposes. Any person liable under reverse charge must register under GST regardless of turnover.
Match GSTR-2B Before You File
GSTR-2B is an auto-generated statement showing every ITC amount available to you based on what your suppliers reported in their GSTR-1 filings. It is not a return; it is a system-generated document to verify your records against the portal.9Goods and Services Tax. FAQs – Viewing Form GSTR-2B
Values from GSTR-2B auto-populate into your GSTR-3B. If a supplier failed to report an invoice in GSTR-1, that credit will not appear in your GSTR-2B, and claiming it anyway in GSTR-3B creates a mismatch that invites scrutiny. Reconciling GSTR-2B with your purchase register every month is the single most effective way to catch problems before they become audit issues. The portal also flags invoices where ITC is restricted under Section 16(4) or place-of-supply rules, so the “ineligible” section deserves the same attention as the eligible amounts.9Goods and Services Tax. FAQs – Viewing Form GSTR-2B
Interest and Penalties When Numbers Go Wrong
Late payment of tax triggers interest under Section 50 of the CGST Act at a rate up to eighteen percent per annum. For returns filed after the due date, interest applies only to the portion of tax paid through the electronic cash ledger, not on the portion covered by ITC.10Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 50 Interest on Delayed Payment of Tax
Wrongly claiming and using ITC costs more. If you avail and utilize credit you were not entitled to, the interest rate rises to up to twenty-four percent per annum on the wrongly claimed amount.10Central Board of Indirect Taxes and Customs. Central Goods and Services Tax Act 2017 – Section 50 Interest on Delayed Payment of Tax That difference is why reconciling before filing is worth the time.
Composition Taxpayers Sit Outside the Credit Chain
The input-output offset described above does not apply to businesses enrolled under the composition scheme. Composition taxpayers pay GST at reduced flat rates but cannot claim ITC on their purchases, and their customers cannot claim ITC on purchases made from them. Before opting in, weigh the tax you save on simplified compliance against the ITC you would forfeit. For businesses with significant taxable purchases, the lost credits often outweigh the administrative convenience.