Two documents, both from the department, routinely showing different figures for the same client. It is the question a junior asks every October and the answer is not that one of them is wrong.
They are records of different things. Form 26AS is a record of tax: what was deducted, collected and paid against the client's PAN, with the deductor and the challan behind each figure. The AIS is a record of information: what various reporters have said about the client, which is a much wider and much looser set.
Treating them as two versions of one document is what produces the confusion. Knowing which question each one answers removes most of it.
What 26AS is a record of
Form 26AS is organised into parts, and each part plays a different role in the return:
Only the first three produce a figure that goes into the computation. The rest are context, and the reported part is the one that generates client conversations rather than entries.
- Tax deducted from the client: the credit, and the income to compare it against
- Tax collected from the client: credit
- The client's own challans: advance tax and self assessment
- Refunds paid during the year
- Information reported about the client, such as SFT entries and GST turnover
- Listed but not claimable: the client's own deductions as a buyer, defaults, 15G and 15H declarations, transactions in kind
The part numbers moved, and the headings did not
This trips up anyone who automates against 26AS, and it is worth knowing even if you only read it by eye.
TRACES has renumbered the parts. Tax Collected at Source appears as PART-V in a February 2023 text export and as PART-VI in the list TRACES publishes for assessment year 2023-24 onwards. Before AY 2023-24 the parts were not numbered at all, they were lettered: PART A, A1, A2, B, C, D, E, F, G and H.
So any check that says "read part V for TCS" is correct for exactly one window of time. The only stable identifier is the title of the part, which has not moved.
The same caution applies to column order. Within a part, the safe way to read a column is by its label, so that a statement with the columns in a different order still reads correctly and an unrecognised label is reported rather than assumed to be something.
Pro tip
If you are reconciling 26AS across several years for one client, expect the structure to change partway through. The lettered layout and the numbered one are the same information under different headings.
Which file to download, and which to leave alone
This is the practical part, and it is where a lot of time is lost.
From TRACES, take the text export. It is complete, it is delimited, and every part comes through intact. It arrives inside a ZIP. The PDF is readable too, but it is a printed document and reading it is line by line work with all the fragility that implies.
From the e-filing portal, take the AIS PDF. The information rows come through, and the tax per deductor comes through wherever the PDF prints it.
Do not build anything on the AIS JSON. The portal offers it for the department's own offline AIS Utility, which decrypts it using a password made from the PAN and the date of birth. The department publishes no format for that file and no supported way to read it outside the utility. Reading it means relying on a key somebody extracted from the utility by hand, which can change at any update. A figure that depends on that is a figure you cannot stand behind in front of a client.
The per-category CSV and Excel downloads are in the same position: convenient, partial, and not what the rest of the return should be built on.
Important
The AIS JSON is encrypted for the department's own utility. Any tool that reads it is relying on a key nobody published, and the figures it produces are only as stable as the next portal update.
Where they genuinely disagree
Most differences between 26AS and the AIS are not errors in either one.
The AIS carries reports from sources that never appear in 26AS, because they are not tax events at all: interest the bank reported, dividends, securities transactions, a property registration. These are information, reported by somebody else, and they can be wrong without anybody having done anything wrong.
26AS carries a status against each entry showing whether the deductor's own return has been processed and the credit booked. A deduction the client can prove with a certificate and that does not yet appear is usually a deductor who has not filed, not a missing payment.
And both can lag. A figure appearing in one and not the other is far more often a timing question than a discrepancy, which is the argument for pulling both again before filing rather than relying on a download taken in July.
The same gross-versus-net trap sits underneath all of it: bank interest with TDS deducted appears in the statement at the net figure and in both of these documents at the gross one.
What to do with a difference
In order, and most differences stop at the first or second step.
First, check whether the two documents are even reporting the same thing. An AIS information row and a 26AS deduction row describe one transaction from two sides, and the amounts are not meant to match.
Second, check the period. A deduction made in March and deposited in April sits in different places depending on which document you are reading and when you pulled it.
Third, check the deductor. A TAN that appears in 26AS with no corresponding entry in the books means an income the client did not mention, which is a conversation rather than a reconciliation.
Only then is it worth raising feedback on the AIS, which is slow and worth saving for the differences that actually change the return.
Conclusion
26AS answers what tax was paid against this PAN and by whom. The AIS answers what the world has reported about this person. A return needs both, and conflating them turns a ten minute check into an afternoon.
The credit side of the computation comes from 26AS, with the TAN and the challan beside each figure, because that is where those live and no bank statement carries a BSR code.
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