“Free” tells you nothing about quality. A free reconciliation tool has to be paid for somehow: by an upgrade you will be pushed towards, by advertising, or by your data. Any of those can be acceptable, but you should know which one you are in before you feed it a client's purchase register. And the cost of a wrong tool is not the licence. Your ITC claim rests on what is communicated in GSTR-2B (Section 16(2)(aa) and Rule 36(4)), and claiming more in GSTR-3B than GSTR-2B shows, beyond the notified limit, brings a DRC-01C intimation that you must answer in Part B.
Choosing a tool? See our guide to GST reconciliation software first.
The ten checks and how to score them
Score 2 when the answer is a clear yes you have seen for yourself, 1 when it is partly true or the tool does not say, and 0 when it is a clear no. Any 0 on check 1 rules the tool out for client data, whatever the total.
| # | Check | Score 2 looks like | Score 0 looks like |
|---|---|---|---|
| 1 | Data handling | Files are processed on your device and it survives the offline test | Files are uploaded, or the page says nothing |
| 2 | Sections of GSTR-2B read | Reads invoices and credit or debit notes and tells you what it read | Reads one table and never says so |
| 3 | Match key | Supplier GSTIN plus invoice number | Invoice number alone |
| 4 | Invoice number tidy-up | Ignores case, spaces, slashes, hyphens and leading zeros, and shows the original text | Exact text match only, or silent guessing |
| 5 | Amount tolerance | A stated, small tolerance, with differences shown | Hidden or wide tolerance |
| 6 | Missing versus IMS Pending | Keeps them in separate buckets and says it cannot see your dashboard | One “not found” pile |
| 7 | Credit and debit notes | Lists them, and says how far it handles them | Ignores them |
| 8 | Duplicates | Flags repeats in your books and counts each once | Double-counts or drops them silently |
| 9 | Export | Full export with status and both sides' amounts | Screen only or a summary PDF |
| 10 | Limits and honesty | States row limits and what it does not do | Claims of perfect accuracy, surprise caps after upload |
Total out of 20: 16 or more is usable; 12 to 15 is a first pass only, with the areas that scored 0 or 1 checked by hand; below 12, leave it. These bands are our own rule of thumb, not an official standard.
Why the less obvious checks matter
Check 1: the offline test
Load the page, switch off your internet connection, add your files and run it. If a report still appears, the matching is happening in your browser. If it fails, look closer. You can also open the Network tab (F12 in Chrome or Edge) during a run and look for a request as large as your file. Analytics requests are small; an upload is not. Your own firm's file is the right one to test with, not a client's.
Check 2: which sections
GSTN's own list of the tables in GSTR-2B includes B2B, B2BA, CDNR and CDNRA. A tool that reads only B2B will show amended invoices as missing and hide every credit or debit note. Ask which tables are read, and whether the list is printed on the results page or hidden in the help text.
Checks 3 and 4: matching
A valid invoice number can carry letters, digits, hyphen and slash, up to sixteen characters, and needs to be unique within the supplier's series for a financial year (Rule 46(b)). It does not have to be unique across suppliers, which is why the key must include the GSTIN. It also means your books and the portal can legitimately spell the same number differently, so a tool has to tidy both sides the same way. Our note on invoice number mismatches shows the usual cases.
Check 5: tolerance
Small rounding differences between your ERP and a supplier's invoice are normal, and a tool should not raise an alarm over a rupee. The danger is the opposite: a tolerance so wide that a real difference of a few hundred rupees passes as matched. Ask what the tolerance is; case 4 and case 5 below test both sides. Our guide to round-off mismatches explains where the small differences come from.
Check 6: missing is not one thing
Records a recipient keeps Pending in IMS do not become part of GSTR-2B, and the action can be changed and GSTR-2B recomputed before GSTR-3B is filed. An invoice absent because you left it Pending needs an IMS action; one absent because the supplier has not filed needs a phone call. Read why invoices get stuck in IMS Pending and what to do when a supplier has not filed. A tool cannot see your live dashboard, so the honest ones say “likely”.
Check 7: credit notes
IMS also lets a recipient keep credit notes Pending, so notes are part of the live ITC picture, not an afterthought. A tool that ignores them is incomplete; one that lists them and says what it does not yet match is at least honest. For the exact IMS options on credit notes, check the current GSTN advisory.
Worked example: a ten-case test
Build a tiny purchase register and a matching GSTR-2B (from your own firm's data) with these ten cases. Every case has a right answer you can check in seconds. Amounts are tax amounts.
| # | Books invoice / 2B invoice | What it tests | Books tax | 2B tax | Right answer |
|---|---|---|---|---|---|
| 1 | GT/26-27/089 / GT-26-27-089 | Slash versus hyphen | ₹7,200 | ₹7,200 | Matched |
| 2 | 000452 / 452 | Leading zeros | ₹14,400 | ₹14,400 | Matched |
| 3 | inv-77a / INV-77A | Letter case | ₹1,800 | ₹1,800 | Matched |
| 4 | SL-104 / SL-104 | Rounding of ₹1 | ₹5,625 | ₹5,626 | Matched or a visible small difference |
| 5 | SL-105 / SL-105 | Real difference | ₹3,000 | ₹2,400 | Value mismatch of ₹600 |
| 6 | SL-106 / not in 2B (supplier has other invoices in 2B) | Missing, supplier present | ₹9,000 | Nil | In books, not in 2B; likely IMS Pending or filed late |
| 7 | SL-107 / not in 2B (supplier not in 2B at all) | Supplier absent | ₹4,500 | Nil | In books, not in 2B; supplier probably has not filed |
| 8 | not in books / SL-108 | Only in 2B | Nil | ₹2,700 | In 2B, not in books |
| 9 | SL-109 entered twice / SL-109 | Duplicate in books | ₹1,200 twice | ₹1,200 | Matched once; second entry flagged, not double-counted |
| 10 | not in books / CN-021 in CDNR | Credit note | Nil | ₹1,350 | Listed as a credit note, not counted as an invoice |
Expected totals: five matched (cases 1 to 4 and 9), one value mismatch (case 5), two in books but not in 2B (cases 6 and 7), one only in 2B (case 8), one duplicate (case 9's second entry) and one credit note (case 10). The ITC at risk is ₹9,000 plus ₹4,500, which is ₹13,500. A tool that gets nine or ten of these right has earned a real trial; one that fails cases 1 to 3 is matching on raw text, and one that reports ₹13,500 as matched has told you something dangerous. To test our tool with case 10, put the credit note in a JSON file; if you use the Excel download, confirm that the credit note appears in the notes list.
Red flags: a request for your GST portal login, an upload with no statement about what happens to the file, a match on invoice number alone, credit notes or amendments silently skipped, a free plan that reveals a row cap only after you upload, and a promise of perfect accuracy without a list of what it does not cover.
How our own tool stands on this list
We built this checklist partly to be marked against. Our tool reads the GSTR-2B Excel or JSON and your register in the browser. From the JSON file it reads the B2B, B2BA, credit and debit note (cdnr) and ISD lists. From the Excel download it reads a sheet named B2B (a sheet named B2BA only if there is no B2B sheet) and a sheet named CDNR, so amended invoices (B2BA) are read from the JSON but not from the Excel file, and if your workbook names its credit-note sheet differently, the notes will not be listed; check that they appear. The CDNRA table is not read at all. It matches on supplier GSTIN and invoice number, ignoring case, punctuation and leading zeros, and treats tax within ₹1 as matched. It reports IMS Pending as a flag (an invoice absent from 2B whose supplier appears elsewhere in it), lists duplicates and credit or debit notes separately, and exports to CSV. It does not connect to the portal, read your live IMS dashboard or reconcile GSTR-2A, and full two-way credit note matching is not built yet. Run the ten cases through it and judge for yourself.
Run the ten-case test on our tool
Open the tool, add your test 2B and register, and compare the five buckets with the right answers above. Your GSTR-2B and purchase register files are read in your browser and never uploaded to any server.
Frequently asked questions
How do I check whether a free reconciliation tool uploads my files?
Load the page, switch off your internet connection, then add your files and run it. If it still produces a report, the matching happens on your device. You can also open the browser's Network tab during a run and look for a request as large as your file.
Is a tool that matches on invoice number alone reliable?
No. Rule 46(b) only requires an invoice number to be unique within the issuing supplier's series for a financial year, so two suppliers can use the same number. A sound match key includes the supplier GSTIN as well as the invoice number.
What score should a free tool reach before I use it in a filing month?
On the scale in this guide, 16 or more out of 20 with no zero on data handling, and a correct result on the 10-case test. Between 12 and 15, use it as a first pass and check the weak areas by hand. Below 12, do not use it for a filing month.
Related guides
- GST reconciliation software: what kinds exist and which fits you
- GSTR-2B matching tool: how automated matching decides two invoices match
- GST reconciliation data privacy: why client data should stay on your machine
- How to use a GSTR-2B reconciliation tool
- TallyPrime's built-in GSTR-2B reconciliation or a free browser tool: which should you use
- GSTR-2B matching in SAP S/4HANA: ingestion, BAPI reconciliation, and GR/IR clearing
- GST portal offline matching tool or a browser tool: which fits your GSTR-2B check
Last checked: 30 Sep 2026. Sources: Notification 39/2021-Central Tax, Notification 40/2021-Central Tax (Rule 36(4)), GSTN advisory on DRC-01C, GSTN FAQ on GSTR-2B tables, GSTN IMS FAQ, GSTN FAQ on GSTR-9 (IMS credit-note options), Rule 46, CGST Rules.