Rule 42 and Rule 43 ITC Reversal: Calculation Guide

How is the Rule 42 credit pool built?

Start with total input and input-service credit for the tax period, then classify it rather than applying a turnover ratio to everything.

The exact algebra and definitions in the current rule control. The practical point is that direct attribution comes before the common-credit ratio.

How is the exempt component calculated?

The ordinary Rule 42 ratio is exempt turnover divided by total turnover in the State/UT, multiplied by common credit. Apply rule-specific values where there is no turnover in the period or a prescribed special method. Review the definition of exempt supply, including supplies on which the recipient pays tax under reverse charge where the Act requires their inclusion.

Example: common credit C2 is ₹120,000, exempt turnover E is ₹2 million and total turnover F is ₹10 million. D1 is ₹24,000. If non-business use exists and the prescribed 5% method applies, D2 is ₹6,000. The illustrative eligible common balance is ₹90,000, subject to every rule condition.

How does the annual true-up work?

Monthly calculations are provisional. Recalculate using annual exempt and total turnover. If the annual reversal exceeds provisional reversals, reverse the shortfall with applicable interest within the rule timetable. If provisional reversal was higher, reclaim the excess in the permitted manner. Preserve the annual workbook and return references.

How does Rule 43 treat capital goods?

Capital goods used exclusively for non-business/exempt activity are ineligible; those used exclusively for taxable/zero-rated supplies are credited subject to conditions. Credit on common capital goods enters the common pool and is spread over 60 months. The monthly common amount is apportioned using the exempt-turnover ratio.

When use changes, the rule contains specific treatment for the remaining useful life. Do not restart a fresh 60-month period merely because accounting classification changed.

What controls make the calculation defensible?

Maintain invoice-level tagging, general-ledger mapping, exempt/taxable turnover reconciliation, State-wise turnover, capital asset register, invoice dates, remaining useful life, return-table mapping and approval for overrides. Tie permanent reversals to Table 4(B)(1) of GSTR-3B as clarified by Circular 170, while temporary reversals follow their distinct reporting route.

What mistakes distort the result?

Common errors are treating exports as exempt, applying the ratio to exclusive taxable credit, omitting blocked ITC, using national instead of State/UT turnover, forgetting annual true-up, applying 60 months from capitalization rather than the prescribed invoice reference, and reclaiming a permanent reversal as though it were temporary.

What should be done each month?

Close invoice tagging before GSTR-3B, reconcile turnover to returns and books, compute Rules 42 and 43 separately, review exceptions, post ledger entries, and retain the signed workbook. At year-end, run the statutory final computation promptly and record any interest analysis.