Every income tax refund in India rests on a single, unglamorous act of bookkeeping: the tax department matching the credit you claim in your return against the credit someone else — an employer, a bank, a client, a buyer — has reported on your behalf. When those two numbers agree, the refund moves in weeks. When they do not, the return does not fail outright; it simply stalls, silently, inside the Centralised Processing Centre's automated matching engine, and the taxpayer is often the last to know why.

A tax credit mismatch is not a niche technical hiccup. It is, year after year, one of the most common reasons ordinary salaried and self-employed taxpayers receive an intimation instead of a refund. Understanding how the matching actually works — and where it typically breaks — turns this from an anxiety-inducing surprise into a five-minute pre-filing check.

The Three Documents That Decide Your Credit

Before a rupee of tax credit reaches your return, it passes through three interlinked statements maintained by the tax department, and a mismatch anywhere in this chain can hold up processing.

● Form 26AS —  Every TDS deducted by an employer, bank or client, every TCS collected on high-value purchases, and every advance or self-assessment tax you deposit is meant to appear here. Crucially, the department's processing system grants credit strictly on the basis of what this statement shows — not on what your salary slip or bank certificate says.

● Annual Information Statement (AIS) —  A far wider financial footprint: salary, interest, dividends, mutual fund and securities transactions, property purchases, and foreign remittances, drawn from banks, registrars, and other reporting entities. It is richer than Form 26AS but is an information layer, not a credit-granting one.

● Taxpayer Information Summary (TIS) —  A summarised, category-wise digest of the AIS, built specifically to help pre-fill your return. It is a convenience layer, and, like AIS, is not the authoritative source for claiming TDS credit.

The practical rule that follows from this architecture is simple but frequently missed: if a TDS entry shows up in AIS or in your Form 16/16A but is absent from Form 26AS, the credit is, for processing purposes, not yet real. It exists in the department's broader information system but not in the ledger the assessment engine actually reconciles against.

Where Mismatches Actually Come From

A mismatch is rarely the taxpayer's error. In most cases, the taxpayer has reported the credit correctly based on the certificate in hand; the break happens one step upstream, in how the deductor or collector filed — or failed to file — their quarterly statement. The table below maps the common patterns.

How the Department Actually Catches It

When you file, the return is first processed under Section 143(1) — a wholly automated comparison between what you have declared and what the department's own records show. If the TDS you have claimed exceeds what is visible in Form 26AS, the processing system does one of two things: it disallows the unmatched portion of the credit and computes tax payable or a reduced refund accordingly, or it holds the return for manual reconciliation, which lengthens the timeline considerably.

A second, less visible mechanism is Section 245: if you have an outstanding demand from an earlier assessment year sitting on record — even one you believe you have already resolved — the department can adjust a current year's refund against it without seeking fresh consent, though you are entitled to be given an opportunity to respond first. Many taxpayers discover an old, forgotten demand only when a current refund arrives smaller than expected, or not at all.

Spotting the Mismatch Before You File

Because the department's engine works off Form 26AS specifically, pre-filing reconciliation should follow a fixed sequence rather than a quick glance at the pre-filled form.

1. Pull all three statements together

Download Form 26AS and AIS/TIS from the e-filing portal only after the fourth-quarter TDS filing deadline (31 May) has passed for the financial year, so late-filed entries have had time to appear. Downloading too early is the single most common reason people believe there is a mismatch when the data is simply not yet updated.

2. Reconcile deduction-by-deduction, not total-to-total

Match each Form 16/16A or TCS certificate line item against the corresponding entry in Form 26AS — same deductor TAN, same quarter, same amount — rather than comparing only the grand totals, which can mask offsetting errors.

3. Treat AIS discrepancies as a feedback opportunity, not a filing input

If AIS shows information you believe is incorrect or duplicated, use the built-in feedback mechanism on the portal to flag it. This does not change your credit claim, but it creates a documented trail that is useful if the entry resurfaces in a notice later.

4. Confirm challans against the correct assessment year

For self-assessment or advance tax paid directly by you, verify the challan identification number, the assessment year selected at the time of payment, and the amount, all of which are common sources of self-inflicted mismatches.

Fixing It: Before You File

If a mismatch surfaces during reconciliation and you have not yet filed, the fix depends on whose error it is.

● Deductor-side error:  Contact the deductor in writing and ask them to file — or correct — the relevant quarterly TDS/TCS return. Once their correction statement is processed, Form 26AS updates typically within a few working days. Claiming the credit before it appears in Form 26AS, purely on the strength of a certificate, invites disallowance at processing.

● Self-paid tax under the wrong assessment year:  File a correction request for the challan through the assessing officer, or use the online challan correction facility where available, quoting the correct assessment year and PAN.

● PAN/Aadhaar or bank validation issues:  If your Aadhaar and PAN are not linked, or your bank account is not pre-validated on the e-filing portal, refunds — even when correctly computed — will not be credited. Both should be verified independently of the credit-matching exercise.

Fixing It: After You've Filed and a Notice Arrives

If the mismatch is caught only after filing — typically through a Section 143(1) intimation showing reduced credit, or a demand instead of the expected refund — the remedy depends on when the underlying data was actually corrected.

If the deductor's correction has since been filed and reflects in Form 26AS

File a rectification request under Section 154 on the e-filing portal, selecting the appropriate reason and re-validating against the now-corrected Form 26AS. Rectification applications can be filed within four years from the end of the financial year in which the original processing order was passed, though acting promptly avoids compounding delay on the refund itself.

If the deductor has still not corrected their filing

A rectification request will not help, because the underlying data the department checks against remains unchanged. The practical route is to keep following up with the deductor while retaining written proof of every request, since this correspondence is often asked for if the matter later needs to be escalated through a grievance.

If you disagree with an adjustment made under Section 245

Respond within the window given on the portal before the adjustment is finalised; once the refund has already been adjusted against a past demand, reopening it requires demonstrating that the earlier demand itself was incorrect or already paid.

If the matter remains unresolved

Raise a structured grievance through the e-Nivaran facility on the portal, or contact the Centralised Processing Centre in Bengaluru directly, attaching the TDS certificate, the deductor's acknowledgement of the correction filed (if any), and the intimation received.

The Refund-Interest Angle Most Taxpayers Miss

A stalled refund is not only a cash-flow inconvenience; it has a defined statutory cost to the department, which works in the taxpayer's favour. Under Section 244A, where a refund arises from excess TDS, TCS, advance tax or self-assessment tax, simple interest of 0.5% for every month or part of a month is payable — broadly 6% annually — computed from 1 April of the assessment year if the return was filed on or before its due date, or from the date of actual filing if it was filed late.

There is one threshold worth knowing before assuming this interest is owed: no interest is payable at all if the refund amount is less than 10% of the tax actually determined as payable for the year. This is why very small refunds sometimes arrive without any accompanying interest, even after a genuine delay.

A Structural Change Worth Watching

Taxpayers reconciling credits for income earned in FY 2025-26 (Assessment Year 2026-27) are still working under the Income-tax Act, 1961, and Form 26AS as it exists today. From Tax Year 2026-27 onward, under the newly effective Income-tax Act, 2025, the same annual tax-credit statement is set to be renamed Form 168, alongside broader terminology changes across the return-filing process. The underlying reconciliation logic — credit is granted on the basis of what the deductor has actually reported — is expected to continue; only the label changes, but it is worth tracking for anyone filing after this transition.

The Underlying Discipline

Tax credit mismatches persist not because the system is opaque, but because most taxpayers treat Form 16 or a bank TDS certificate as the final word, when the department treats Form 26AS as the only word. The gap between those two documents — created upstream by a deductor's filing, not by the taxpayer's declaration — is where refunds stall. A taxpayer who reconciles deduction-by-deduction before filing, understands which errors belong to whom, and knows the exact rectification and grievance channels available, converts what looks like a bureaucratic risk into a routine, three-statement checklist completed once a year.

This article is for general information on Indian income tax procedure and is not a substitute for advice from a qualified chartered accountant or tax professional on your specific facts.