The PMT-06 due date for August 2026 is 25 September 2026, a Friday — and it catches out more small businesses than almost any date in the GST calendar, because it is a payment date, not a filing date. If your business is on the Quarterly Return Monthly Payment (QRMP) scheme, you file your GSTR-1 and GSTR-3B once a quarter, but you still deposit tax every month through a simple challan in Form GST PMT-06. August is the second month of the July–September quarter, so August’s tax is due on 25 September — long before the quarterly return is anywhere near due.
What the PMT-06 due date for August 2026 actually covers
The GST portal describes the scheme in one line: the QRMP scheme is “for eligible taxpayers to file their Form GSTR-1 and Form GSTR-3B returns on quarterly basis, while paying their tax dues on monthly basis through a challan.” It is open to taxpayers “whose aggregate annual turnover (PAN based) is up to ₹ 5 Crore” — which is most small and mid-sized businesses. The appeal is obvious: two returns a quarter instead of six. The part that gets forgotten is the second half of the sentence — paying their tax dues on monthly basis.
For the first two months of every quarter, the portal is explicit: “Payment can be made in the first two months by a simple challan in FORM GST PMT-06,” and “the due date for making payment by challan is 25th of the next month.” The third month’s tax is settled when you file the quarterly GSTR-3B. So the July–September quarter runs like this:
| Month | How the tax is paid | Due |
|---|---|---|
| July (month 1) | PMT-06 challan | 25 August 2026 |
| August (month 2) | PMT-06 challan | 25 September 2026 |
| September (month 3) | With the quarterly GSTR-3B | On the quarterly return |
That middle row is the one due now. Miss it and nothing bounces back at you immediately — there is no return to file, no portal error — which is exactly why it slips. The cost shows up quietly, as interest, and it is worth understanding how the two payment methods change that exposure.
The two ways to work out what to pay
The portal offers two methods for the monthly PMT-06, and the choice matters more than it looks.
Fixed Sum Method. Here the system hands you a pre-filled challan — “commonly also known as 35% challan” — set at “35% of amount paid as tax from electronic cash ledger in their return for the preceding quarter.” Its real value is the safe harbour attached to it: the portal states that “no interest would be payable in case the tax due is paid in the first two months of the quarter by way of depositing auto-calculated system generated challan… by the 25th of the succeeding month.” Pay the auto-calculated amount on time and that month carries no interest, even if your actual liability for the month turned out higher.
Self Assessment Method. Here you pay “the actual tax due… through challan, in Form GST PMT-06, by considering the tax liability on inward and outward supplies and the input tax credit available for the period as per law.” It reflects the real month, which suits a business whose turnover swings — but there is no auto-calculated safe harbour, so a short payment leaves the shortfall exposed to interest under the general GST provisions.
| Method | How the amount is set | Interest position |
|---|---|---|
| Fixed Sum (35% challan) | System pre-fills 35% of last quarter’s cash tax | No interest if the auto challan is paid by the 25th |
| Self Assessment | You compute the month’s actual liability after ITC | Shortfall exposed to interest under GST law |
There is no late fee on the monthly PMT-06 payment — the portal confirms “there is no late fee for delayed payment of tax for any of the first two months.” That is not the same as free. The late fee lives on the quarterly return; the cost of a missed monthly payment is interest, and it runs whether or not anything on the portal reminds you.
What to do before 25 September
Three things settle it. First, confirm whether you are actually on QRMP — a business under ₹5 crore that opted in files quarterly but must still raise the monthly challan; if you are unsure which scheme you are on, that is the first thing to check, because it changes every due date this month. Second, pick your method deliberately: if last quarter was representative and cash flow is steady, the fixed-sum challan buys you the interest safe harbour for the price of a click; if the month was unusually light or heavy, self-assessment keeps you honest but puts the interest risk back on your own numbers. Third, generate and pay the PMT-06 challan by 25 September — not on it — so a bank delay does not push it into the 26th.
The QRMP scheme is a genuine simplification: fewer returns, less monthly filing friction, and one of the better things the GST Council has done for small businesses. But it trades filing frequency for a payment discipline that is easy to lose, precisely because the monthly step is a challan and not a return. The PMT-06 due date for August 2026 — 25 September — is the reminder that on QRMP, quarterly is how often you file, not how often you pay.