Reverse charge mechanism (RCM) audit testing

Testing reverse charge mechanism compliance means confirming the client correctly identified which inward supplies attract RCM, raised the self-invoice the law requires where the supplier is unregistered, paid the RCM liability in cash through the electronic cash ledger rather than offsetting it against available input tax credit, and claimed the matching input credit in the same or an appropriate later period rather than missing it or claiming it too early. Cash payment is non-negotiable under the GST law structure; the other three are commonly where the actual errors sit.

Which supplies attract RCM

The list of supplies and services notified under reverse charge is set by notification under the CGST Act and the corresponding state and integrated enactments, and it has been amended multiple times since 2017 — additions, removals and clarifications have all happened. Do not rely on memory or on a list from a prior year's file for the current notified position; pull the current notifications and any amendments for the year under audit before starting the test.

• Specified supplies from an unregistered person to a registered person, within categories the law and notifications define — this is not a blanket reverse charge on all unregistered purchases, and treating it as one is a common client-side error in both directions.
• A defined list of services notified for reverse charge regardless of the supplier's registration status — categories like goods transport agency services, certain legal services, services of a director to the company, and sponsorship services have all appeared on this list at various points, each with its own conditions.
• Supplies notified under section 9(4) / the equivalent import-of-service provisions, including import of services from outside India, which is reverse charge by its nature.
• Sector- or category-specific notifications that apply to only some clients — real estate promoters receiving from unregistered suppliers is a frequently missed one for clients in that sector.

Self-invoicing

Where the supply is received from an unregistered supplier and attracts reverse charge, the recipient is required to issue a self-invoice, since there is no registered supplier to issue a tax invoice that the recipient can hold. This is frequently the step mid-market clients skip entirely — the RCM liability gets computed and paid from the accounting entries, but no self-invoice document exists in the file.

• Check whether self-invoices are being generated at all for RCM supplies from unregistered persons, as a population, not just for the sampled transactions.
• Where self-invoices exist, check the numbering is sequential and distinguishable from the client's regular outward tax invoices.
• Check the self-invoice date against the time-of-supply rules for RCM, since the liability and the credit period both key off this date, not off the date the expense was recorded in the books.

Testing that RCM liability was paid in cash

This is the highest-value single test in an RCM audit, because the error is both common and mechanical to detect, and because it is a cash-flow and penalty exposure if missed. RCM liability must be discharged through the electronic cash ledger; it cannot be set off against input tax credit available in the electronic credit ledger, including credit arising from the same RCM supply.

1. 01Extract the RCM liability reported in each period's GSTR-3BTable 3.1(d) of GSTR-3B captures inward supplies liable to reverse charge. This is the liability figure to trace through to payment.
2. 02Trace each period's RCM liability to the electronic cash ledgerThe cash ledger extract from the GST portal shows deposits and the heads (tax, interest, fee, penalty) against which they were utilised. The RCM tax liability for the period should be discharged against a cash deposit under the relevant tax head, not shown as nil with the liability apparently vanishing through an offset.
3. 03Confirm the credit ledger was not used to pay the RCM liability itselfGSTR-3B's own structure is supposed to prevent this, but errors still occur, particularly where a client's accounting entries net the RCM liability and the matching credit against each other in a single journal with no separate cash payment visible underneath.
4. 04Reconcile the cash paid under RCM across the year to the RCM expense baseTotal RCM-attracting expenditure for the year, at the applicable rate, should approximate the total cash paid under RCM for the year, adjusted for timing. A material gap with no explanation is the signal to investigate specific periods.
5. 05Check for interest exposure on delayed RCM paymentRCM liability not paid in the period it arose, and settled later, generally attracts interest from the original due date. Confirm whether any identified late payments were accompanied by interest, and if not, quantify the exposure.

Testing the matching input credit and its timing

Once RCM tax is paid in cash, the payer is generally entitled to claim the equivalent amount as input tax credit, subject to the usual eligibility conditions, including that the supply itself is not blocked under section 17(5). This credit does not come through GSTR-2B the way a regular supplier-reported credit does, because there is no supplier return generating it — it is self-assessed based on the RCM payment the recipient itself made.