How to Reverse ITC Under GST Rule 42 and 43

To reverse input tax credit under GST Rule 42 and 43, you split your credit into pools, isolate the credit used exclusively for exempt or non-business purposes, and then proportionately reverse the common credit that serves both taxable and exempt supplies. Rule 42 of the CGST Rules, 2017 handles inputs and input services using the formula D1 = (E/F) x C2 plus a deemed D2 of 5% of C2, while Rule 43 spreads capital goods credit over a 60-month life and reverses Te = (E/F) x Tm each month. Both flow from Section 17(2) and 17(3) of the CGST Act, 2017, are reported in GSTR-3B Table 4(B)(1), and are trued up once a year with interest payable under Section 50 on any short reversal. This guide explains every variable, the timing, and two full worked examples in rupees so you can compute the figure correctly the first time.

What Is ITC Reversal Under Rule 42 and 43?

ITC reversal under Rule 42 and 43 is the proportionate write-back of common input tax credit when inputs, input services, or capital goods are used partly for taxable supplies and partly for exempt supplies or non-business purposes. The portion that relates to exempt or non-business use is not yours to keep, so the law makes you add it back to your tax liability instead of claiming it as credit.

The logic sits at the heart of how GST works. Input tax credit exists to remove tax on tax along a chain of taxable supplies. When the chain breaks, because the output is exempt or the input is consumed privately, the credit no longer has a taxable supply to offset. Rule 42 and Rule 43 are the machinery that measures exactly how much credit has fallen out of the taxable chain in a given period and pushes it back. Rule 42 deals with inputs and input services, which are consumed within the period. Rule 43 deals with capital goods, which deliver value over years, so their credit is reversed slowly across a deemed 60-month life rather than all at once.

Because the reversal is proportionate, it depends on two moving numbers: how much of your credit is common (used for both taxable and exempt supplies) and what share of your turnover is exempt. A business that sells only taxable goods has nothing to reverse. A business that mixes taxable sales with exempt activity, interest income, or real estate has a reversal every period. The more exempt your turnover, the larger the slice of common credit you give back. This is why accurate turnover splitting matters as much as the formula itself.

Why the Law Requires a Reversal: Section 17(2) and 17(3)

Section 17(1) restricts credit where goods or services are used partly for business and partly for other purposes. Section 17(2) restricts credit where supplies are partly taxable (including zero-rated) and partly exempt. Read together, they establish that credit follows taxable business use only. Rule 42 and Rule 43 simply translate that principle into arithmetic for the credit you cannot directly attribute to one side or the other. Understanding the two definitions below is the foundation for every calculation that follows.

Exempt Supply (Section 17(3))

An exempt supply, for reversal purposes, is any supply that does not carry output GST and so cannot absorb input credit. Under Section 17(3), the value of exempt supply includes wholly exempt and nil-rated supplies, non-taxable supplies, supplies on which the recipient pays tax under reverse charge, the sale of land, the sale of a completed building, and transactions in securities valued at 1% of their sale value. Each of these adds to E, the exempt turnover that drives the reversal. A frequent and costly error is treating exports as exempt; they are zero-rated, not exempt, and carry full credit.

Common Credit (C2)

Common credit is input tax credit that cannot be tied to a single supply because the underlying input, service, or capital good serves both taxable and exempt activity at once. Rent on a shared office, audit fees, telephone bills, and shared machinery all generate common credit. The formula does not touch credit you can directly attribute to taxable supplies (T4) or to exempt supplies (T2); it acts only on the genuinely common pool, denoted C2 under Rule 42. Getting the boundary between exclusive and common credit right is what separates a defensible reversal from an estimate that invites a notice.

Rule 42 vs Rule 43: Which One Applies?

The first decision in any reversal is whether the credit sits under Rule 42 or Rule 43. The dividing line is the nature of the purchase: inputs and input services fall under Rule 42, while capital goods, defined in Section 2(19) as goods capitalised in the books and used in business, fall under Rule 43. The table below contrasts the two rules across the parameters that matter in practice.

A single business often applies both rules in the same month. A pharmaceutical maker reverses common credit on shared utilities under Rule 42 and, separately, reverses the monthly slice of credit on a shared production line under Rule 43. The two reversals are computed independently but both land in Table 4(B)(1) of the same GSTR-3B. Treating them as one figure, or applying the input formula to a machine, is a common source of mismatch during scrutiny.

Decision Table: How Each Purchase Is Treated

Before any formula, decide which pool each purchase belongs to. The decision table below maps the use of an input or capital good to its credit treatment, which is the step most businesses rush and later regret.

The Rule 42 Formula for Inputs and Input Services

Rule 42 reads as a sequence of subtractions that strip out the credit you cannot keep, leaving a common pool on which a single ratio is applied. The notation looks dense, but each letter has a plain meaning. The table below defines every variable, after which the three computation steps put them to work.

Step 1: Segregate the Exclusive Credits

Start with T, the total input tax on inputs and input services for the month. From it, carve out the three buckets of credit you can never use: T1 for inputs used exclusively for non-business or personal purposes, T2 for inputs used exclusively to make exempt supplies, and T3 for credit blocked under Section 17(5), such as certain motor vehicles, food and beverages, and works contracts for immovable property. These three amounts are reversed or simply not availed; they leave the calculation before the common pool is built. Accurate tagging here is decisive, because anything misfiled as common will be over- or under-reversed downstream.

Step 2: Find the Common Credit

Subtract the three exclusive buckets to get C1 = T - (T1 + T2 + T3), the credit that legitimately enters your electronic credit ledger. From C1, remove T4, the credit tied exclusively to taxable and zero-rated supplies, which is fully eligible and needs no reversal. What remains is the common credit, C2 = C1 - T4. C2 is the pool that serves both taxable and exempt supplies at the same time, such as credit on shared rent, audit fees, and utilities. Only C2 is subject to the proportionate reversal; nothing else in the period is touched by the ratio.

Step 3: Apportion and Reverse

Now apply the ratio. D1 = (E/F) x C2 is the slice of common credit that relates to exempt supplies, where E is the aggregate value of exempt supplies in the period and F is the total turnover in the State. Separately, D2 = 5% of C2 is the deemed slice attributable to non-business use of common inputs. The sum D1 + D2 is the amount you reverse in the month. The balance, C3 = C2 - (D1 + D2), stays in your ledger as eligible common credit. Eligible ITC for the period is therefore T4 plus C3, while T1, T2, and T3 never formed part of your usable credit at all.

Worked Example: Rule 42 Monthly Reversal

Numbers make the formula concrete. Take Sunrise Foods Ltd., a manufacturer registered in Karnataka that makes both taxable packaged snacks and nil-rated unbranded grains, with the following figures for the May 2026 tax period. The company tags every purchase to its use before touching the formula, which is the discipline that keeps the reversal defensible.

The computation runs in three moves. First, C1 = T - (T1 + T2 + T3) = ₹10,00,000 - (₹50,000 + ₹1,00,000 + ₹50,000) = ₹8,00,000. Second, the common credit C2 = C1 - T4 = ₹8,00,000 - ₹5,00,000 = ₹3,00,000. Third, with an exempt ratio of E/F = ₹40,00,000 / ₹2,00,00,000 = 20%, the reversals are D1 = 20% x ₹3,00,000 = ₹60,000 and D2 = 5% x ₹3,00,000 = ₹15,000. The total Rule 42 reversal for May 2026 is D1 + D2 = ₹75,000, reported in GSTR-3B Table 4(B)(1).

The retained eligible credit is C3 = C2 - (D1 + D2) = ₹3,00,000 - ₹75,000 = ₹2,25,000. Adding back the directly attributable taxable credit T4 of ₹5,00,000, Sunrise Foods keeps ₹7,25,000 of credit on inputs and input services for the month. The ₹2,00,000 sitting in T1, T2, and T3 was never usable, and ₹75,000 of common credit is given back through the formula. This single calculation, repeated monthly and trued up once a year, is the whole of Rule 42 in practice.

The Rule 43 Formula for Capital Goods

Capital goods are different because they are not consumed in one period. A machine bought today serves output for years, so reversing its entire credit in the month of purchase would be unfair, and claiming all of it when part of the output is exempt would be wrong. Rule 43 solves this by deeming a useful life of 60 months from the invoice date and reversing only the slice that relates to exempt supplies, period by period.

Capital Goods Used Exclusively

The simplest cases need no formula. A capital good used exclusively for taxable or zero-rated supplies carries full credit with no reversal. A capital good used exclusively for exempt supplies, or exclusively for non-business or personal purposes, gets no credit at all; any credit taken is reversed in full. The formula only engages when a capital good is genuinely common, serving both taxable and exempt supplies at the same time, which is the realistic position for shared plant, buildings, and equipment.

Common Capital Goods: The 60-Month Method

For a common capital good, take Tc, the ITC availed on that asset, and spread it across the useful life: the monthly slice is Tm = Tc / 60. Where multiple common capital goods are in use, the aggregate of all their monthly slices is Tr. The reversal for the tax period is Te = (E/F) x Tm (or Te = (E/F) x Tr for the aggregate), added to your output tax liability each month. Because E and F change every month, Te is recomputed each period using that month's turnover ratio. The reversal continues for the full 60 months; after the 60th month, no further reversal is required even if the asset still serves exempt supplies.

Change of Use: From Taxable to Common

A capital good can move from exclusive taxable use into common use, for example when a line that made only taxable products starts producing an exempt variant. Rule 43 handles this by counting the months already elapsed since purchase and applying the slice only to the remaining useful life. The credit attributable to the period of exclusive taxable use stays, but the reversal for the months the asset has been common is added to output tax liability with interest. This prevents a business from front-loading full credit and then quietly shifting an asset to exempt production.

Worked Example: Rule 43 Capital Goods Reversal

Continue with a capital good owned by the same business. Sunrise Foods bought a shared packaging and grading line in April 2024 for ₹40,00,000 plus 18% GST, giving an ITC (Tc) of ₹7,20,000. The line processes both taxable snacks and nil-rated grains, so it is a common capital good from day one. The figures below compute the reversal for the May 2026 tax period.

The monthly slice is Tm = ₹7,20,000 / 60 = ₹12,000. With an exempt ratio of 20% for May 2026, the reversal is Te = 20% x ₹12,000 = ₹2,400, added to output tax liability and reported in Table 4(B)(1). If June 2026 has a higher exempt ratio of 25%, the June reversal rises to ₹3,000 on the same ₹12,000 slice, because Te tracks the current month's turnover. The line was bought in April 2024, so its 60-month window runs to March 2029; Sunrise Foods reverses a recomputed Te every month until then, after which the asset drops out of the reversal entirely.

Over the full useful life, the business gives back only the part of the machine's credit that supported exempt output, not a rupee more. If the line were ever used exclusively for taxable snacks for a stretch of months, the exempt ratio for those months would be lower and the reversal smaller, automatically. This self-adjusting design is why Rule 43 spreads the credit rather than reversing it in a lump, and why a fixed asset register that tracks each asset's invoice date and ITC is essential to getting Tc and the 60-month clock right.

The Annual Recalculation and True-Up

The monthly reversals under Rule 42 and Rule 43 are provisional. They use each month's turnover, which can swing sharply, so the law requires a single recalculation once the financial year is complete and the real, full-year ratio is known. Rule 42(2) and Rule 43(2) set out this true-up, and skipping it is one of the most common reasons a clean monthly record still ends with a demand.

How the Annual True-Up Works

After the financial year ends, recompute the reversal using the aggregate exempt turnover and aggregate total turnover for the whole year, applied to the total common credit of the year. Compare this annual figure with the sum of your twelve monthly provisional reversals. If the annual figure is higher, you reversed too little during the year and must add the shortfall to output tax liability with interest. If it is lower, you reversed too much and can reclaim the excess as credit, without interest, in a GSTR-3B of the next year. The recalculation must be done before the return for September of the next financial year, and aligned with the Section 16(4) time limit this falls on or before 30 November of the next financial year, with the final position disclosed in the GSTR-9 annual return.

Interest on Short Reversal

Interest is the part businesses underestimate. Where the annual true-up reveals a shortfall, interest runs at 18% per annum under Section 50 from the due date of the return in which the reversal was due to the date you actually pay. Suppose the true-up for FY 2025-26 shows a required reversal that exceeds your monthly reversals by ₹1,00,000, and you pay it 90 days after the due date. The interest is ₹1,00,000 x 18% x 90/365 = ₹4,438, on top of the ₹1,00,000 itself. A larger or longer shortfall scales the cost quickly, which is why a careful monthly estimate is cheaper than a year-end correction.

How to Report ITC Reversal in GSTR-3B

There is no separate return for Rule 42 and 43. The reversal is reported inside your monthly GSTR-3B, in the input tax credit section. Getting the right figure into the right row keeps your eligible credit accurate and avoids a variance against your books. The table below maps the relevant rows of Table 4.

Your Rule 42 reversal (D1 + D2) and your Rule 43 reversal (Te) both sit in Table 4(B)(1), which is the permanent bucket, because reversal for exempt and non-business use is final and not reclaimable like a Rule 37 reversal. Keep Table 4(B)(1) separate from Table 4(B)(2): mixing a permanent Rule 42 reversal into the reclaimable row, or vice versa, distorts your credit position and is a frequent reconciliation error. Our step-by-step GSTR-3B filing guide walks through Table 4 row by row.

What Counts as an Exempt Supply (and What Does Not)?

Because the entire reversal turns on E, the exempt turnover, the most expensive mistakes are about classification, not calculation. The single biggest trap is treating zero-rated supplies as exempt. Exports and supplies to SEZ units are zero-rated under Section 16 of the IGST Act and carry full credit; they are deliberately excluded from E so that exporters are not penalised. Treating them as exempt inflates the reversal and silently surrenders credit you were entitled to keep.

The treatment of financial income deserves attention. Interest on deposits, loans, and advances is an exempt supply, but for taxpayers other than banks and financial institutions, the value of such interest is generally excluded from F, which keeps the reversal proportionate to genuine business turnover. The value of securities transactions enters E at just 1% of sale value, not the full sale price. These nuances move the exempt ratio materially, so confirm the current position on gst.gov.in before locking E and F for the period.

Step-by-Step: How to Calculate and Reverse Common ITC

The full process runs across 8 steps, from classifying purchases to completing the annual recalculation. Most businesses finish the monthly computation in well under one working day once the reconciliation and turnover working are in place. Keep your purchase register, fixed asset register, and turnover split open beside you, and confirm the previous period's GSTR-3B is filed.

Step 1: Classify Every Input, Input Service, and Capital Good by Use

Go through the purchase register and tag each inward supply by its use: exclusively taxable, exclusively exempt, exclusively non-business, blocked under Section 17(5), or common. Separate inputs and input services (Rule 42) from capital goods (Rule 43), because they follow different mechanics. This classification under Section 17(2) decides everything that follows, so base it on actual use, not on a rough guess, and keep a note of the basis for any judgment calls.

Step 2: Segregate the Exclusive Credits (T1, T2, T3)

From the total input tax T on inputs and input services, isolate T1 for exclusively non-business use, T2 for exclusively exempt use, and T3 for credit blocked under Section 17(5). These never enter your usable credit. Confirm T3 against the Section 17(5) list carefully, because credit on items like passenger vehicles, food, and works contracts for buildings is blocked regardless of how the rest of your business uses it.

Step 3: Compute the Common Credit (C1 and C2)

Calculate C1 = T - (T1 + T2 + T3), the credit allowed into your electronic credit ledger. Then remove T4, the credit used exclusively for taxable and zero-rated supplies, to reach the common credit C2 = C1 - T4. Double-check that T4 truly relates only to taxable output; any taxable-attributable credit left inside C2 will be partly reversed needlessly, costing you eligible credit.

Step 4: Calculate the Exempt Turnover Ratio (E/F)

Build E, the aggregate value of exempt supplies in the period, and F, the total turnover in the State. Exclude exports and SEZ supplies from E because they are zero-rated. Add the sale of land or buildings, and 1% of any securities sale value, to E. The ratio E/F is the proportion of common credit that must be reversed, so it is worth rebuilding from the trial balance rather than reusing last month's figure.

Step 5: Apply the Rule 42 Formula (D1 and D2)

Compute D1 = (E/F) x C2, the exempt-attributable common credit, and D2 = 5% of C2, the deemed non-business slice. Add them to get the monthly Rule 42 reversal. The retained eligible common credit is C3 = C2 - (D1 + D2). If the business has no non-business use of common inputs, D2 still applies as a deemed figure unless you can show the common pool is wholly business-related.

Step 6: Apply the Rule 43 Capital Goods Formula (Tm and Te)

For each common capital good, take its ITC Tc and compute Tm = Tc / 60. Sum the slices across all common capital goods to get the aggregate, then reverse Te = (E/F) x Tm for the period. Add Te to output tax liability. Track each asset's 60-month clock from its invoice date so it drops out of the reversal the month the useful life ends.

Step 7: Report and Pay the Reversal in GSTR-3B Table 4(B)(1)

Enter the combined reversal, D1 + D2 from Rule 42 and Te from Rule 43, in Table 4(B)(1) of GSTR-3B for the period, alongside any Section 17(5) blocked credit. The portal nets it against Table 4(A) so only eligible credit reaches Table 4(C). File GSTR-3B by the 20th of the next month (or the 22nd or 24th for QRMP filers) using DSC or EVC.

Step 8: Complete the Annual Recalculation by 30 November

After the year ends, recompute the reversal on full-year E and F under Rule 42(2) and Rule 43(2), and compare it with your total monthly reversals. Pay any shortfall with interest under Section 50, or reclaim any excess, by the return for September of the next year, aligned with the 30 November deadline. Disclose the final reconciled reversal in your GSTR-9 annual return.

If you are unsure which action a particular credit needs, run through this quick checklist before you file:

1. Is the credit blocked under Section 17(5)? If yes, it is T3, fully removed, with no further calculation.
2. Is the input used only for taxable or zero-rated supplies? If yes, it is T4, fully eligible, no reversal.
3. Is it used only for exempt or only for non-business purposes? If yes, it is T2 or T1, fully excluded.
4. Is it a capital good serving both taxable and exempt supplies? If yes, apply Rule 43: Tm = Tc / 60 and Te = (E/F) x Tm.
5. Is it a common input or service? If yes, apply Rule 42: reverse D1 + D2 and retain C3.

Other ITC Reversal Rules You Should Know

Rule 42 and 43 are the most formula-heavy reversals, but they are not the only ones. A business can trigger multiple reversals in the same period for different reasons, and confusing them leads to wrong reporting. The most frequently searched is the supplier-default reversal, which has nothing to do with exempt supplies. The table below places the main reversal rules side by side.

The supplier-default reversal under Rule 37A is a frequent point of confusion because it sounds like Rule 42 but works in reverse: it is about whether the supplier discharged the tax, not about how you used the input. Reviewing your inbound records carefully each cycle helps you catch both kinds of issue early; our guide on accepting and rejecting invoices in the GST IMS explains how supplier records reach your credit in the first place. For the full spread of monthly and annual GST work, IncorpX GST services cover reconciliation, reversal computation, and return filing together.

Common Mistakes That Trigger Notices and Interest

Beyond the arithmetic, a handful of habits account for most reversal disputes. Each is avoidable with a fixed monthly routine and a clear turnover working.

1. Treating Exports as Exempt

Exports and SEZ supplies are zero-rated, not exempt. Adding them to E inflates the reversal and surrenders credit you are entitled to keep. Keep zero-rated turnover in a separate column and out of E entirely, every period.

2. Reversing Capital Goods in One Shot

Capital goods follow the Rule 43 60-month method, not the full reversal of Rule 42. Reversing the whole Tc at once overstates liability; forgetting the monthly Te understates it. Track each asset's slice and its 60-month clock in the fixed asset register.

3. Skipping the Annual True-Up

Monthly provisional reversals rarely sum to the annual figure. Without the Rule 42(2) and 43(2) recalculation, a shortfall accrues interest at 18% per annum and an excess is forfeited. Diarise the true-up for the next year's October to November window.

4. Mixing the GSTR-3B Reversal Rows

Rule 42 and 43 reversals are permanent and belong in Table 4(B)(1). Putting them in the reclaimable Table 4(B)(2), where Rule 37 sits, distorts your credit position and triggers reconciliation mismatches at GSTR-9.

The Cost of Getting ITC Reversal Wrong

The reversal itself carries no government fee; it is part of your normal GSTR-3B. The real cost lands when the reversal is wrong, and it is entirely avoidable. The table below sets out where the money goes when common credit is mishandled.

The economics favour getting it right monthly. A ₹1,00,000 shortfall paid 90 days late costs ₹4,438 in interest alone, and a missed reversal discovered in a departmental review can add a penalty on top. Over-reversal is just as wasteful: credit you surrendered by mistake is locked until the annual true-up, and only if you remember to reclaim it. You can sanity-check the GST on a purchase or sale with our GST calculator while building the turnover working, and align the annual reversal with your GSTR-9 annual return filing so the two figures never diverge.

Related Resources

• How to File GSTR-3B Online: where the Rule 42 and 43 reversal is reported in Table 4(B)(1).
• How to File GSTR-9 Annual Return: the annual return that discloses the final reconciled reversal.
• How to File GSTR-9C Reconciliation Statement: reconciling credit and turnover for audit-threshold taxpayers.
• How to Accept or Reject Invoices in GST IMS: how supplier records become your input tax credit.
• GST Calculator: check tax on inputs and outputs while preparing the turnover working.

Summary

Reversing input tax credit under GST Rule 42 and 43 comes down to one principle: credit follows taxable business use, so the part serving exempt or non-business activity must be given back. Under Rule 42, split your credit into pools, find the common credit C2, and reverse D1 = (E/F) x C2 plus D2 = 5% of C2. Under Rule 43, spread capital goods credit at Tm = Tc / 60 and reverse Te = (E/F) x Tm each month for 60 months. Report both in GSTR-3B Table 4(B)(1), keep zero-rated supplies out of E, and recompute on full-year turnover by 30 November of the next financial year, paying interest at 18% per annum on any shortfall under Section 50. Done as a monthly routine and trued up once a year, the reversal stays accurate, defensible, and free of interest.