It is 15 October 2026. You have downloaded the September GSTR-2B and added up the tax. The purchase register says ₹8,46,300 and the 2B says ₹6,85,470. Your owner asks where ₹1,60,830 went. Most of it did not go anywhere: the register and the 2B were never built to agree, and the useful question is which part of the gap is a loss, which part is a timing difference, and which part is your own booking error.
This page is one part of our GSTR-2B reconciliation guide, which shows how the whole process fits together.
This post is about the summary level, where you compare two totals and explain the difference. For matching bill by bill, see how GSTR-2B reconciliation works. The summary bridge comes first because it tells you how much invoice-level work is waiting.
Compare tax with tax, for the same month
Three choices decide whether the two totals can be compared at all.
- Use tax, not invoice value. ITC is the tax component. Add IGST, CGST and SGST (and cess, if you deal in cess goods) on both sides. Comparing the register's gross bill total with the 2B's tax total is the most common reason a first attempt looks hopeless.
- Take the 2B side from every table. The Excel you download from the portal carries B2B, B2BA, CDNR and CDNRA. Add the tax on invoices and debit notes and deduct credit notes. Lines in the amendment tables (B2BA, CDNRA) refer to a document reported earlier, so look at them one by one instead of adding them blindly.
- Cut the register the way the portal cuts the 2B. Your register is cut by the date you booked the bill; the 2B is cut by when the supplier reported it. GSTR-1 for a monthly filer is due on the 11th and the 2B is generated on the 14th. The cut-off is explained in the GSTR-2B freeze date guide.
Nine reasons the totals differ
Every gap between a register and a 2B comes from one of the causes below, or from a mix of them. Test them in this order, because the first two account for most of the money.
| Cause | Effect on the gap | What usually explains it | Look here first |
|---|---|---|---|
| Booked, not in 2B | Books higher | Invoice number or GSTIN typed differently; invoice Pending in IMS; supplier reported late or not at all | Invoice number formats, then IMS Pending, then the supplier |
| In 2B, not booked | 2B higher | Bill reached accounts late; bill belongs to another GSTIN of yours; supply not received | Goods receipt records |
| Same invoice, different tax | Either way | Supplier reported another value or rate; rounding | Supplier's invoice copy |
| 2B marks ITC not available | Books higher | The 2B line carries a reason code | The reason column on the 2B line |
| Booked twice | Books higher | One entry from the goods receipt, one from the supplier's bill | Same supplier and number, two vouchers |
| Credit and debit notes | Either way | Note in 2B not yet booked, or booked in another month | Credit notes in IMS |
| Amended documents | Either way | Register holds the original, 2B holds the amendment | Amended invoices |
| Reverse charge purchases | Books higher | Tax you booked and pay yourself; no supplier line in the 2B (an unregistered supplier files no GSTR-1) | RCM matching |
| Rounding | Small, either way | Paise-level differences across many invoices | Round-off mismatches |
Two of these need a caution. First, a booked invoice missing from the 2B is not proof that the supplier defaulted. Under IMS a recipient can keep an invoice Pending, and Pending records are not part of the 2B. If that is the cause, changing the action and recomputing the 2B before you file GSTR-3B brings the credit in. Second, the credit you may take is capped by the 2B, not by your books: Rule 36(4) allows no ITC on invoices whose details have not been communicated in GSTR-2B, and Section 16(2)(aa) says the same about the supplier's GSTR-1.
Worked example: a ₹1,60,830 gap explained
A trading company compares its September 2026 register with the GSTR-2B generated on 14 October 2026. The register shows total tax of ₹8,46,300 on purchases booked in September. The 2B shows ITC available of ₹6,85,470. There are no amendments this month, so that line is left out. The bridge starts at the books total and ends at the 2B total.
| Line | What it is | Effect | Running total |
|---|---|---|---|
| 0 | Tax per purchase register, September | Nil | ₹8,46,300 |
| 1 | Three invoices from two suppliers booked, not in the 2B | −₹1,12,500 | ₹7,33,800 |
| 2 | One invoice booked twice (goods receipt and supplier bill) | −₹18,000 | ₹7,15,800 |
| 3 | Services from an unregistered supplier, booked under reverse charge | −₹42,000 | ₹6,73,800 |
| 4 | Two invoices in the 2B, goods received in September, bills unbooked | +₹36,900 | ₹7,10,700 |
| 5 | Supplier credit note in the 2B, not yet booked | −₹9,000 | ₹7,01,700 |
| 6 | One invoice: books tax ₹27,000, supplier reported ₹24,300 | −₹2,700 | ₹6,99,000 |
| 7 | One matched invoice, 2B line marked ITC not available | −₹13,500 | ₹6,85,500 |
| 8 | Rounding across the register (residual) | −₹30 | ₹6,85,470 |
| Tax per GSTR-2B, ITC available | Nil | ₹6,85,470 |
The arithmetic closes: eight adjustments, of which seven reduce the total and one increases it, move ₹8,46,300 to ₹6,85,470, a net movement of ₹1,60,830. Now the bridge can be read as a to-do list rather than a single scary number.
| Line | Amount | Credit at risk this month? | What to do |
|---|---|---|---|
| 1 | ₹1,12,500 | Yes | Check number and GSTIN first, then IMS, then the supplier. If IMS was the cause, accept and recompute before filing GSTR-3B. |
| 2 | ₹18,000 | No, it was never credit | Reverse the second voucher in the books. |
| 3 | ₹42,000 | Not a 2B item | Take it through your reverse charge working, not through the 2B. |
| 4 | ₹36,900 | No | Book the bills. The credit is already in the 2B. |
| 5 | ₹9,000 | Reduces credit | Book the credit note; check whether IMS lets you hold it. |
| 6 | ₹2,700 | Yes | Claim the 2B figure of ₹24,300 and ask the supplier to correct the value. |
| 7 | ₹13,500 | Yes | Read the reason on the 2B line; do not claim until it is resolved. |
| 8 | ₹30 | No | Nothing to do. |
Credit genuinely at risk is lines 1, 6 and 7 together: ₹1,12,500 + ₹2,700 + ₹13,500 = ₹1,28,700. That is a smaller and more precise number than ₹1,60,830, and it tells the owner which suppliers to call.
Do not file GSTR-3B on the books total. If this company claimed ₹8,46,300 against a 2B of ₹6,85,470, it would be claiming credit the 2B does not carry. An excess over the notified limit draws a DRC-01C intimation, and Part B of that form is mandatory. Interest at 18% a year applies on credit wrongly availed and utilised. The reply process is in the DRC-01C guide.
Rules that make the bridge trustworthy
Freeze both totals before you start. Note the date and time you downloaded the 2B. If you change IMS actions and recompute, the 2B changes and the bridge has to be redone. Also fix the register cut: same month, same GSTIN, same tax heads.
Never plug the residual. A rupee or two per hundred invoices is rounding. A residual of ₹30 on ₹8,46,300 is fine; a residual of ₹4,000 means a line is missing or wrongly signed, and it is usually a duplicate or a credit note. Section 170 rounds tax amounts to the nearest rupee, but the law does not fix a matching tolerance; that is a working rule of your own.
Keep the bridge with the return. When 3B ITC exceeds 2B ITC beyond the limit, the GSTN advisory says filing DRC-01C Part B to reconcile the difference is mandatory. A dated bridge with invoice numbers behind each line is exactly the working paper that reply needs. For the wider month plan, see the 14th-to-20th timeline.
Where gstr2bmatch.in fits
The tool does not build the bridge for you, but it produces the invoice lists that fill most lines. It matches on supplier GSTIN and invoice number, ignoring case, spaces, special characters and leading zeros, and treats a tax difference of up to ₹1 as a match. Bucket C and E together are line 1 (the report's "ITC at risk" figure is exactly these two, using tax from your books). The duplicates list is line 2 and bucket D is line 4. Bucket B carries the Diff column for line 6. Matched rows show a note such as "ITC not available" with the reason code (line 7). Three limits to know as of 30 Sep 2026: the credit and debit note list shows note number, date and type but not the amount, so take line 5 from the 2B itself; in the exported CSV, bucket D rows carry the 2B tax in the Tax (Books) column, so sum that column for line 4; and with the Excel 2B download the tool reads the B2B sheet, so use the JSON download if amendments matter to your gap.
Get the invoice lists behind your bridge
Upload the 2B and your register and read off buckets C, E, D and B in rupees. Your GSTR-2B and purchase register files are read in your browser and never uploaded to any server.
Related guides
- GSTR-2B reconciliation guide: the complete guide to ITC matching
- GSTR-2B reconciliation with purchase register: matching your register with GSTR-2B invoice by invoice
- Invoices in GSTR-2B but not in my books: how to investigate them
- GSTR-2B tax amount mismatch: why the tax differs and how to fix it
- How accountants can automate GSTR-2B reconciliation
- GSTR-2B not generated or not showing: what to check and what to do
- GSTR-2B Table 4D mismatch: unmatched invoices and fixes
Last checked: 30 Sep 2026. Sources: CGST Act, section 16, CGST Rules, Rule 36(4) (notification 40/2021-CT), GSTN IMS FAQ, GSTN advisory on DRC-01C, GSTN return user guide (GSTR-2B generation), GSTR-1 user manual, GSTN FAQ on comparison of liability declared and ITC claimed, CGST Act, section 170, Notification 13/2017-Central Tax (interest rate).