Input Service Distributor (ISD) Under GST: Now Mandatory from April 1, 2025
ISD registration is no longer optional. If your clients have multiple GSTINs under the same PAN and receive common service invoices at the Head Office — they must comply now or face ITC disallowance, penalties, and audit scrutiny.
1. What Is an Input Service Distributor (ISD)?
An Input Service Distributor under GST is, at its core, a Head Office — or any designated office — that receives tax invoices for input services that are used across multiple branches of the same business. Because those branches may be in different states with separate GSTINs, the HO cannot simply keep all the ITC — it must distribute it to the right branches in the right proportions.
Think of it this way: a large manufacturing company pays ₹10 lakh annually for accounting software used by its factories in Gujarat, Maharashtra, and Tamil Nadu. The annual subscription invoice comes to the HO in Delhi. The GST paid on this invoice — let’s say ₹1.8 lakh — is an ITC that belongs to all three factories in proportion to their usage. The ISD mechanism is the formal legal pathway for making that distribution happen correctly under GST.
Before April 2025, companies had a choice: use the ISD mechanism, or simply raise a cross-charge invoice between the HO and branches. Many preferred cross-charge for its simplicity. That flexibility is now gone — at least for third-party procured input services.
2. Why Did ISD Become Mandatory from April 2025?
The 50th GST Council Meeting in July 2023 set the direction: ISD would become mandatory. The Finance Act 2024 gave it statutory teeth by amending Section 2(61) and Section 20 of the CGST Act. The operative notification — No. 16/2024-Central Tax dated August 6, 2024 — set the effective date as April 1, 2025.
Why did the government act? Because the old regime was creating problems at scale:
- ITC mismatches: When HOs availed full ITC on shared services and didn’t distribute it properly, GSTR-2B at the branch level didn’t match actual ITC claims — triggering system-generated scrutiny notices.
- Revenue leakage: In some cases, businesses were claiming ITC at the HO without distributing it to branches that had taxable outward supplies, effectively mis-routing credits.
- Inconsistent cross-charge practices: Different businesses were applying cross-charge in wildly different ways — some distributing at cost, some at market value — creating non-uniformity and audit disputes.
- Audit readiness: A formal ISD mechanism with GSTR-6 creates a clean, auditable trail of how ITC on common services is allocated — far easier for departmental verification.
3. Who Needs ISD Registration? Eligibility Criteria
ISD registration is mandatory for a business unit if all three of the following conditions are met:
- It is an office of a supplier of goods or services (typically the HO, but can be any office)
- It receives tax invoices for input services (not goods, not capital goods)
- Those input services are used by, or for the benefit of, more than one GSTIN under the same PAN
There is no turnover threshold. A startup with two state GSTINs that pays a shared SaaS subscription at its registered office must comply just as much as a ₹500 crore conglomerate.
Who is NOT required to register as ISD?
- Businesses with only a single GSTIN (no distribution needed)
- Composition taxpayers (cannot register as ISD)
- Businesses where all common invoices are received directly by each branch (no centralized procurement)
- Distribution of ITC on goods or capital goods — ISD mechanism does not apply to these
4. ISD vs Cross Charge — The Critical Difference in 2025
This is the most common point of confusion among CAs advising multi-location clients. The two mechanisms are not interchangeable after April 1, 2025. Understanding which applies where is now a compliance prerequisite.
✅ Input Service Distributor (ISD)
- For third-party procured input services
- HO receives invoice from external vendor
- Distributes ITC via ISD invoice (not a tax invoice)
- No GST charged on ISD invoice
- Based on turnover ratio formula (Rule 39)
- Mandatory from April 1, 2025
- GSTR-6 filing required monthly
- Examples: Software fee, legal fee, audit fee
⚡ Cross Charge
- For internally generated inter-branch services
- One branch provides services to another branch
- A tax invoice must be raised (supply between distinct persons)
- GST is charged on the cross-charge invoice
- Valued at open market value or cost-plus
- Continues to apply for internal services
- No separate return; reported in GSTR-1
- Examples: HR services, IT support, management services
5. ITC Distribution Formula Under ISD (Rule 39)
Rule 39 of the CGST Rules governs how an ISD distributes ITC to recipient branches. The formula is proportional — based on the turnover of recipient branches in the preceding financial year. If the preceding year’s data is unavailable (e.g., new branches), the current year’s actual turnover is used.
Worked Example
M/s InfoTech Pvt Ltd has its Head Office in Bengaluru (ISD). It pays ₹5 lakh per year for a cloud software subscription used by its three branches:
| Branch | State | Annual Turnover (₹) | Proportion | ISD Credit (18% GST on ₹5L = ₹90,000) |
|---|---|---|---|---|
| Branch A | Delhi | ₹1.5 crore | 37.5% | ₹33,750 |
| Branch B | Chennai | ₹1.5 crore | 37.5% | ₹33,750 |
| Branch C | Kolkata | ₹1 crore | 25.0% | ₹22,500 |
| Total | ₹4 crore | 100% | ₹90,000 |
IGST vs CGST/SGST — How ISD Handles Tax Type
This is a detail many CAs miss. When distributing credit, the type of GST distributed depends on whether the recipient is in the same state or a different state than the ISD:
- Same state as ISD: Distribute CGST as CGST + SGST as SGST
- Different state from ISD: Distribute both CGST and SGST as IGST
- IGST available with ISD: Distribute as IGST to all — same state or different state
6. ISD Registration Process — Step by Step
7. ISD Invoice: What It Must Contain
An ISD invoice is not a tax invoice. It does not charge GST — it transfers already-availed ITC to recipient branches. Rule 54(1) of the CGST Rules specifies the mandatory fields:
| Field | Details |
|---|---|
| Document heading | “Input Service Distributor Invoice” or “Input Service Distributor Credit Note” |
| Name, address, GSTIN of ISD | Mandatory — must match ISD registration details |
| Serial number | Unique consecutive serial number for each financial year |
| Date of issue | Date the ISD invoice is issued to the recipient |
| Name, address, GSTIN of recipient | Each recipient branch gets a separate ISD invoice |
| Amount of credit being distributed | Separate amounts for IGST, CGST, SGST/UTGST |
| Eligible vs ineligible ITC | Must separately show eligible and ineligible ITC distributed |
| Signature/digital signature | Authorised signatory of the ISD |
8. GSTR-6 Filing — Complete Walkthrough
GSTR-6 is the monthly GST return filed by the ISD. It is due by the 13th of the following month. There is no annual return requirement for ISDs (no GSTR-9). Here is what GSTR-6 contains and how to file it correctly:
| Table | What to Report | CA Action Required |
|---|---|---|
| Table 3 | Details of ITC received by the ISD (auto-populated from GSTR-2B) | Verify auto-populated data against purchase register |
| Table 4 | ITC available for distribution (eligible vs ineligible) | Classify ITC as eligible/blocked under Section 17(5) |
| Table 5 | ITC distributed to each recipient GSTIN | Enter amounts per Rule 39 formula; split by IGST/CGST/SGST |
| Table 6 | ITC to be re-credited to ISD (e.g., credit notes) | Adjust for vendor credit notes received during the month |
| Table 7 | Late fees payable (if any) | ₹50/day for delay (₹20/day for nil return) |
The GSTR-6A Connection
Recipient branches will see the distributed ITC auto-populated in their GSTR-6A once the ISD files GSTR-6. They must then claim this ITC in their GSTR-3B (the credit is not automatically transferred). CAs should remind client finance teams to reconcile GSTR-6A data before filing GSTR-3B to ensure no credit is missed.
9. RCM + ISD: New Game Changer from April 2025
One of the most significant — and least-discussed — changes brought by the April 2025 amendments is that ITC on Reverse Charge Mechanism (RCM) transactions can now be distributed through the ISD. Previously, RCM-related ITC had to stay at the entity that paid the RCM tax; it could not be redistributed via ISD.
This changes the compliance landscape for many businesses. A common scenario: the HO of a company pays legal services fees to an overseas consultant. Under RCM, the HO pays IGST and avails ITC. Under the new rules, if those legal services benefit multiple branches, that RCM-ITC can and must be distributed through ISD.
The practical action: CAs should audit all RCM payments made at the HO level and determine whether those services benefit multiple branches. If yes, ensure the ISD distributes the corresponding RCM-ITC through GSTR-6 — failing which, branches cannot claim that credit.
10. Penalties for Non-Compliance
Recipient branches lose the right to claim ITC distributed informally (without ISD). ITC already claimed may be reversed with interest.
Interest on wrongly availed ITC: 18% p.a. if availed but not utilised; 24% p.a. if availed and utilised — under Section 50 CGST Act.
₹50/day of delay for non-nil returns. ₹20/day for nil GSTR-6 returns. Accrues until the date of actual filing.
Non-compliance with mandatory ISD increases GSTN risk score, triggering automated notices and departmental scrutiny under Section 61/65.
11. CA’s Client Checklist — ISD Readiness Audit
Use this checklist before and after April 1, 2025 to ensure your multi-GSTIN clients are ISD-compliant:
| # | Check Point | Status |
|---|---|---|
| 1 | Has the client identified all GSTINs under the same PAN? | ✅ / ❌ |
| 2 | Are any common input service invoices received centrally at HO? | ✅ / ❌ |
| 3 | Has ISD registration been obtained via GST REG-01 (Serial No. 14)? | ✅ / ❌ |
| 4 | Have all vendors been informed of the new ISD GSTIN? | ✅ / ❌ |
| 5 | Is accounting software updated to handle ISD invoice series separately? | ✅ / ❌ |
| 6 | Has preceding FY turnover of all branches been compiled for Rule 39 formula? | ✅ / ❌ |
| 7 | Are ISD invoices being issued in the correct format per Rule 54(1)? | ✅ / ❌ |
| 8 | Is GSTR-6 being filed by the 13th of each month? | ✅ / ❌ |
| 9 | Are recipient branches reconciling GSTR-6A before claiming ITC in GSTR-3B? | ✅ / ❌ |
| 10 | Are RCM payments at HO reviewed for ISD distribution eligibility? | ✅ / ❌ |
12. Case Study: IT Services Company with 4-State Operations
Client Profile: A mid-size IT services company with HO in Hyderabad and delivery centres in Pune, Chennai, and Noida — each with its own GSTIN. Annual aggregate turnover: ₹42 crore.
The Problem Before April 2025: The company had been raising cross-charge invoices from the HO to each delivery centre for a portfolio of shared services — cloud infrastructure (AWS/Azure), legal retainers, and group health insurance. The cross-charge values were based on the finance team’s internal allocation model, not the Rule 39 turnover formula. This worked until recently.
What Changed: The CA’s team conducted an ISD readiness audit in January 2025 and found that the cloud infrastructure cost and the legal retainer (both procured from external vendors) were in fact third-party input services — making them subject to mandatory ISD distribution from April 2025. The group health insurance, however, was blocked under Section 17(5)(b) — so no ITC was available on it anyway.
Actions Taken: (1) The company registered as ISD at the Hyderabad HO in February 2025. (2) AWS and the legal firm were notified to update their GST invoices to the new ISD GSTIN. (3) The finance team pulled all four branches’ FY 2023-24 turnover figures to pre-compute the Rule 39 ratios. (4) The accounting system was configured with an ISD invoice series and GSTR-6 auto-reminders. (5) The cross-charge methodology was retained only for internally generated HR and management services between the HO and delivery centres.
Result: April 2025 onward — zero disruption. Branches correctly see ISD credit in GSTR-6A and claim it in GSTR-3B. The company is audit-ready, risk score on GSTN has remained low, and no compliance notices have been received.
🔗 Official Resources
- CBIC Official Website — Notification No. 16/2024-Central Tax
- GST Portal (gst.gov.in) — ISD Registration (GST REG-01)
- GST Portal Tutorial — GSTR-6 Filing Guide
- CGST Rules — Rule 39 (ISD Distribution) and Rule 54(1) (ISD Invoice)
- ICAI Indirect Tax Committee — Guidance Note on ISD Mechanism
13. Frequently Asked Questions
What is Input Service Distributor (ISD) under GST?
An ISD is an office — typically the Head Office — that receives tax invoices for input services shared across multiple branches with different GSTINs under the same PAN. It distributes the eligible ITC on those services to branches in proportion to their turnover, via ISD invoices, after filing GSTR-6 monthly. From April 1, 2025, this registration is mandatory.
Is ISD registration mandatory from April 1, 2025?
Yes. Notification No. 16/2024-Central Tax dated August 6, 2024, along with amendments to Sections 2(61) and 20 of the CGST Act by Finance Act 2024, makes ISD registration and compliance mandatory from April 1, 2025. The earlier option of using only cross-charge for third-party input services is no longer legally sufficient.
What is the difference between ISD and Cross Charge under GST?
ISD distributes ITC on externally procured input services using ISD invoices (no GST charged). Cross Charge applies to internally generated inter-branch services, requires a tax invoice with GST, and is reported in GSTR-1. From April 2025, ISD is mandatory for third-party services; Cross Charge continues for internally generated services.
How is ITC distributed under ISD in GST?
Under Rule 39 of CGST Rules, ITC is distributed in proportion to the turnover of each recipient branch as a percentage of total turnover of all recipient branches in the preceding financial year. CGST/SGST is distributed as IGST to out-of-state branches. The ISD must distribute credit in the same month it is received.
What is GSTR-6 and when is it due?
GSTR-6 is the monthly ISD return reporting ITC received by the ISD and its distribution to branches. It is due by the 13th of the following month. Late fee is ₹50/day. There is no annual GSTR-9 filing obligation for ISDs. Recipient branches see the distributed credit in their auto-populated GSTR-6A and claim it in GSTR-3B.
Can ISD distribute ITC on RCM transactions after April 2025?
Yes. This is a new feature introduced by the April 2025 amendments. Previously, RCM-ITC could not be distributed through ISD. Now, ITC on reverse charge mechanism services (e.g., legal fees paid to overseas consultants, GTA services) can be distributed through ISD to branches that benefit from those services.
What happens if a business does not register as ISD despite being eligible?
Non-compliance consequences include: ITC disallowance for recipient branches, interest at 18-24% per annum on wrongly claimed ITC, GSTR-6 late fees, higher GSTN risk scores triggering automated notices, and potential Section 65 departmental audit. Retroactive registration may not cure ITC already incorrectly claimed without proper ISD distribution.
Does Your Client Have Multiple GSTINs? Act Now.
Our team at ClearTax Advisors specialises in ISD registration, ITC distribution structuring, GSTR-6 compliance, and cross-charge vs ISD advisory for CA firms and multi-location businesses across India.
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