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Check Phone Number Using GSTN State Codes and Landline City Codes
Check phone number using GSTN state codes: compare the first two GSTIN digits with a landline’s city code to catch wrong branches, agents and typos.
GST Identification Number
27ABCDE1234F1Z0
- Legal nameSample Traders Pvt Ltd
- StateMaharashtra (27)
- RegistrationActive
- Phone+91 98XXX XXXXX
- Emailc****@example.com
Illustrative result. Request a sample format for live records.
Reading time 7 min
Last reviewed October 2026
Check phone number using GSTN data with one small trick that most people overlook: the first two digits of every GSTIN name the state where the business is registered, and the city code at the start of every landline names the area where that line is installed. When the two point to the same place, the number fits the registration. When they point to different states, something needs explaining, and the explanation usually tells you whether you have the right business, the wrong branch or somebody else entirely.
This guide shows how to run that cross-check, gives a reference table for the commonest states and cities, explains the legitimate reasons for a mismatch, and adds a few other quick consistency tests you can apply to any phone number linked to a GST registration.
Quick answer
- The first two digits of a GSTIN are the state code of the registration.
- A landline’s city code shows where the line is installed.
- When state and city disagree, check for a branch, a neighbouring city or an agent.
- Mobile numbers carry no reliable location, so this check applies to landlines.
- Use the additional places of business in the GST record to explain mismatches.
The Two Codes You Are Comparing
GST state codes are two-digit numbers assigned to each state and union territory. Some of the most frequently seen are 07 for Delhi, 27 for Maharashtra, 29 for Karnataka, 33 for Tamil Nadu, 36 for Telangana, 24 for Gujarat, 19 for West Bengal, 09 for Uttar Pradesh, 06 for Haryana, 08 for Rajasthan and 32 for Kerala. Every GSTIN begins with one of these codes.
Landline city codes, also known as STD codes, are assigned to geographic areas and are written after a leading zero when dialled within India. Large metros have short codes, such as 11 for Delhi, 22 for Mumbai, 44 for Chennai, 80 for Bengaluru, 40 for Hyderabad and 33 for Kolkata. Smaller cities have three- or four-digit codes, such as 141 for Jaipur or 484 for Kochi.
Running the Cross-Check
Take the GSTIN and read its first two digits. Take the landline, strip the country code and leading zero, and read the city code at the start. Then ask whether that city lies in that state. A Karnataka GSTIN with a number beginning 80 fits. A Tamil Nadu GSTIN with a number beginning 44 or 422 fits. A Gujarat GSTIN with a number beginning 22 does not, because 22 is Mumbai.
The check takes seconds and needs no tools beyond a list of codes, which you can keep beside your desk or build into a spreadsheet. It works best as a screen: rows that fit can move on, and rows that do not go into a short pile for a second look.
Legitimate Reasons for a Mismatch
Many mismatches have innocent explanations. The commonest is a branch: the business is registered in one state but also operates an office, warehouse or plant in another, and the number belongs to that location. If so, the GST record often lists the other location as an additional place of business, or the business holds a separate GSTIN in that state under the same PAN.
The second is a neighbouring city across a state border. The national capital region is the classic case: a business registered in Delhi may have an office in Gurugram, which is in Haryana and uses code 124, or in Noida, which is in Uttar Pradesh and uses code 120. Similar patterns occur around other border towns.
The third is a head office elsewhere. Companies sometimes publish a central number at headquarters even for registrations in other states. The fourth is less innocent: the number belongs to an agent, consultant or a different business altogether.
Need the contact behind a GSTIN?Get the sample format with verified business contact fields.
Using the GST Record to Settle a Mismatch
Open the public record for the GSTIN and look at the additional places of business. If one lies in the city that matches the phone’s code, the mismatch is explained: you have the number of that branch. Record it against the branch rather than the principal place of business.
If no listed place matches, search by the PAN to see whether the same business holds another GSTIN in the state the number points to. If it does, the number may belong to that registration instead, and you should move it there. If neither search explains the mismatch, ask the business directly which location the number serves.
Why Mobiles Are Excluded
Mobile numbers do not carry dependable location information. Number portability lets people keep their numbers when they change operators, and people keep their mobiles when they move cities. A mobile first issued in one state may now be used by a trader in another. Do not use a mobile’s digits to judge where a business is; use the GST address instead.
That said, other checks still apply to mobiles: they should have ten digits beginning with 6, 7, 8 or 9, and they should not appear against many unrelated GSTINs.
Other Quick Consistency Checks
A few more tests round out the picture. A number that appears against many unrelated GSTINs is probably an intermediary’s. A landline whose city code matches the state but not the city, for example a different district altogether, may belong to a dealer or a branch not listed in the record. A number that has more or fewer than ten digits after cleaning has been mistyped.
None of these checks needs the business to cooperate, and all can run on a whole list at once in a spreadsheet. Together they catch most of the problems that would otherwise surface as wrong calls.
Want to see real match quality?See the sample format for your own GST numbers.
Three Worked Examples
A wholesaler’s GSTIN begins 33, so it is registered in Tamil Nadu, and the landline on its letterhead begins 422. That is Coimbatore, which lies in Tamil Nadu, so the number fits and the row moves on.
A trading company’s GSTIN begins 07, Delhi, but the number on file begins 124. That is Gurugram in Haryana. The GST record lists no Haryana place of business, but a search by PAN shows a second GSTIN beginning 06 for the same company. The number belongs to the Haryana registration, so it is moved there, and the Delhi row is marked as still needing a local number.
A manufacturer’s GSTIN begins 24, Gujarat, yet the only landline begins 22, Mumbai. There is no Maharashtra place of business and no sibling GSTIN. A short call reveals that the number belongs to a selling agent in Mumbai who handles the manufacturer’s orders. The number is kept, labelled as the agent’s line, and a direct factory contact is requested.
Building the Check Into a Spreadsheet
Create a small lookup table of state codes with their states, and another of the city codes you see most often with their states. Add columns to your list that extract the first two digits of each GSTIN and the city code of each landline, look both up, and flag rows where the states differ. Over time, extend the city code table as new codes appear in your data. The result is a reusable screen you can run on every new list in minutes.
Have a list of GSTINs?Send a few and we will return matching contact fields.
Related guides
Check Contact Number From GST Number When Your Systems Disagree: a related guide.
Discover mobile number from GST number: a related guide.
Frequently Asked Questions
How can I check phone number using GSTN details?
Compare the GSTIN’s first two digits, the state code, with the city code at the start of the landline. If the city lies in that state, the number fits the registration.
What are some common GST state codes?
Examples include 07 Delhi, 27 Maharashtra, 29 Karnataka, 33 Tamil Nadu, 36 Telangana, 24 Gujarat, 19 West Bengal, 09 Uttar Pradesh, 06 Haryana and 32 Kerala.
Why might a correct number have a different state's city code?
It may belong to a registered branch, a neighbouring city across a state border, or a head office elsewhere.
Can I use this check for mobile numbers?
No. Mobiles carry no reliable location because of portability and people moving, so use the GST address instead.
How do I explain a mismatch using the GST record?
Look at the additional places of business, then search by PAN for sibling GSTINs in the state the number points to.
Can this check run on a whole list?
Yes. Extract both codes with spreadsheet formulas, look up their states and flag rows where they differ.
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Disclaimer: GST To Phone Number is an independent data service. We are not affiliated with, endorsed by or connected to the Goods and Services Tax Network, the Central Board of Indirect Taxes and Customs, or any government department. GSTIN verification should always be confirmed against the official GST portal. Contact data is provided for legitimate business use and must be used in line with applicable telecom, privacy and data-protection rules.