A worked example: 10 days late, a normal return
A GSTR-3B return filed 10 days late, with tax liability to report, attracts a total late fee of ₹500 (₹50/day × 10 days), split as ₹25 CGST plus ₹25 SGST per day.
A nil return costs less: same 10 days, no tax liability
The identical 10-day delay for a nil return (no sales, purchases, or tax to report) attracts a lower ₹200 total (₹20/day × 10 days) — a distinct, smaller per-day rate for returns with nothing to declare.
The cap: 150 days late still tops out at ₹5,000
A normal return left 150 days late would raw-calculate to ₹7,500 (₹50 × 150) — but the fee is capped at ₹5,000, so any delay beyond 100 days for a normal return adds nothing further. A nil return's cap is lower still, at ₹500.
Why the per-day rate and the cap both matter
For a short delay, the per-day rate drives the cost — 30 days late on a normal return comes to ₹1,500, well under the ₹5,000 cap. Past a certain point, though, the cap takes over entirely and the fee stops growing no matter how much later the return is filed — the two rules apply at different stages of the same delay.