Every business that outgrows its founder's memory hits the same wall. Deadlines stop being remembered and start being missed, and the first sign is usually a notice rather than a reminder.
What follows is not a complete statutory calendar — those exist and nobody reads them. It is the short list of recurring obligations that cause genuine damage when they slip, and a view on who should own each.
Monthly
TDS deposit — 7th of the following month. Late deposit runs interest at 1.5% per month from the date of deduction. This is the most frequently missed date in Indian business and the easiest to automate.
GSTR-1 — 11th. Outward supplies. Late filing here blocks your customers' input credit, which turns a compliance issue into a commercial one.
GSTR-3B and payment — 20th. The summary return and the actual cash. Interest runs on late payment of tax.
Quarterly
Advance tax — 15 June, 15 September, 15 December, 15 March. Cumulative 15%, 45%, 75%, 100%. Interest under the old Sections 234B and 234C — now 424 and 425 — runs at 1% per month and applies even if you settle everything by 31 March.
TDS returns — 31 July, 31 October, 31 January, 31 May. Form 24Q for salary, 26Q for everything else. A late-filing fee of ₹200 per day runs until filed, and your vendors cannot see their credit until you do.
Annual
The LUT — before your first export of the financial year. If any part of your revenue comes from outside India, this is the one with the worst cost-to-effort ratio in the entire calendar. One form, filed once a year, and it cannot be backdated.
ITR — 31 July for non-audit cases, 31 October where audit applies. Beyond the obvious, the due date governs whether you can carry forward losses.
GSTR-9 annual return — 31 December.
Who should own what
This is the part most businesses get wrong. Deadlines fail not because nobody knew, but because everybody assumed someone else had it.
Assign it explicitly
- Payment dates — TDS deposit, GST payment, advance tax — should sit with whoever controls the bank account. They are cash events, not filing events.
- Return filing — GSTR-1, 3B, TDS returns, ITR — sits with your accountant or advisor.
- The annual items — LUT, GSTR-9 — need a named owner, because annual tasks are the ones that fall through. Nobody has a habit for something that happens once.
- Reconciliation — AIS and 26AS against your own records — should happen quarterly, not in July.
Deadlines fail not because nobody knew, but because everybody assumed someone else had it.
Two practical suggestions
Put the dates in a shared calendar with a named owner on each event and a reminder five working days ahead — not on the day, when there is no time to fix a problem.
And run a quarterly reconciliation against AIS and Form 26AS. The department's view of your income is available to you throughout the year. Discovering a mismatch in July, when the return is due, is the expensive way to find out.
A calendar like this takes an hour to set up and removes an entire category of avoidable cost. If you would rather it sat with someone whose job it is to watch it, that is what a compliance retainer buys — not filing, but the absence of surprises.
This article is general guidance as at 20 May 2026 and is not advice on any specific situation. References reflect the Income-tax Act, 2025 (in force from 1 April 2026), the CGST and IGST Acts as amended, and GST rates effective 22 September 2025. Please obtain advice on your own facts before acting.