The Head Office Bill Everyone Shared: Why Input Service Distributor Registration Turned Mandatory in 2025

A Mumbai-headquartered engineering services firm we will call "Meridian Systems" ran offices in three states, each with its own GSTIN. Every month the head office received invoices for things the whole company used together: the statutory audit fee, a pan-India advertising campaign, and annual software subscriptions billed to the Mumbai office.

All of these vendors put the Mumbai GSTIN on the invoice. So the entire input tax credit (ITC) landed in the Mumbai books. The Delhi and Bengaluru offices, which genuinely benefited from these services, saw none of that credit. For years the accountant simply raised a monthly cross-charge invoice from Mumbai to the branches to push some of the tax across. It felt workable, until it wasn't.

The GST problem they faced

Under the amended law, distributing the credit of common input services through the Input Service Distributor (ISD) mechanism is no longer optional. With effect from April 2025, Section 20 of the CGST Act read with Rule 39 makes ISD registration mandatory where an office receives tax invoices for input services that are attributable to more than one distinct GSTIN of the same PAN.

Meridian's cross-charge shortcut created two risks. First, credits of common third-party services were being retained fully at Mumbai instead of being distributed proportionately to each state that consumed them. Second, a cross-charge is meant for internally supplied services between branches, not for merely passing on the tax on a vendor's bill. Mixing the two invited a mismatch during any audit and a possible denial of credit at the branch level.

The finance head realised that if a departmental query landed, the branches could lose ITC they were rightfully entitled to, and the Mumbai office could be questioned for holding excess credit.

How they solved it correctly

Meridian took a clean, structured route.

Step 1: Take a separate ISD registration

The Mumbai head office applied for a distinct ISD registration under the same PAN. An ISD registration is separate from the normal GSTIN, even in the same state.

Step 2: Route common service invoices to the ISD

They instructed vendors of shared services, the auditor, ad agency and software provider, to bill the ISD registration going forward.

Step 3: Distribute credit through GSTR-6

Each month the ISD distributes the eligible credit to Mumbai, Delhi and Bengaluru in the ratio of their respective turnover, exactly as Rule 39 prescribes, and files GSTR-6 by the 13th of the following month. The receiving branches then see the credit auto-populate.

Step 4: Keep cross-charge only for genuine internal services

Where the Mumbai team actually performed work for a branch, such as shared HR or management support, they continued raising a proper tax invoice. This kept the two mechanisms cleanly separated.

Within two return cycles, the credit was flowing to the right states and the branch-level ITC was healthy again.

The key lesson for readers

If your business operates under one PAN across multiple states, and a single office receives bills for services the whole organisation uses, you almost certainly need an ISD registration now. Do not rely on a cross-charge to move third-party input service credit. Cross-charge is for services one branch supplies to another; ISD is for distributing the credit on common vendor invoices. Using the wrong tool leaves credit stranded or exposed.

Also remember: ISD covers input services, not goods, and the distribution must follow the turnover-based ratio in the relevant period.

How GSTClear helps

GSTClear flags when your credit pattern suggests an ISD is required, helps you set up and manage the ISD registration, and prepares GSTR-6 distributions in the correct turnover ratio automatically. It reconciles the distributed credit against each branch's GSTR-2B so nothing goes missing, and keeps your genuine cross-charge invoices separate and audit-ready.

If your head office is quietly hoarding common service credit while your branches starve, act before an audit forces the issue. Set up your ISD workflow on GSTClear today and let every rupee of credit reach the state that earned it.

FAQ

Is ISD registration mandatory for every business with more than one GSTIN?

It is mandatory where one office receives tax invoices for common input services used by multiple GSTINs under the same PAN. If you never receive such shared-service invoices, you may not need it, but most multi-state businesses do.

Can I use ISD to distribute credit on goods?

No. The ISD mechanism applies only to input services. Credit on goods must flow through normal invoicing or a genuine supply between branches.

What return does an ISD file and by when?

An ISD files GSTR-6 monthly, generally by the 13th of the following month, showing the credit received and how it was distributed to each recipient GSTIN.