Why this is the highest-stakes annual deadline
This is where your full year's tax position gets reconciled. Any shortfall in what monthly TDS or advance tax installments covered during the year becomes due at this point, and any documentation gaps from earlier in the year become visible all at once. Businesses that keep monthly bookkeeping current generally find this a straightforward reconciliation; those that reconstruct a year of records in the final weeks find it a much bigger project than the deadline itself suggests.
D-01 or D-02 — it depends on your turnover
Which specific return form applies, and what it actually requires, depends on your turnover tier and entity type. See our D-01 vs D-02 guide for how to tell which one applies to your business before you start preparing it.
Advance tax installments don't replace this filing
If your business pays estimated tax in installments through the year, that's credited against your final liability — it isn't a substitute for the annual return itself. The return is still where everything gets reconciled, including any gap between what was paid in installments and what's actually owed.
The Poush-end extension exists — but confirm it applies to you
A further extension to Poush-end is generally available for those who need it, but availability and conditions can vary by year and circumstance. Don't assume it applies automatically to your specific filing — confirm current-year availability with IRD or an accountant before you plan around it.