When you register for GST, you get a GSTIN and a welcome email and the vague feeling that you've done something official. What nobody explains clearly is what happens next — and what the consequences are if you don't keep up with it.
Here's the honest version.
What GST registration actually commits you to
Once registered, you have to file GST returns every month, regardless of whether you made any sales. Even a nil return has to be filed. Miss it and you get a late fee of ₹50 per day (₹20 per day for nil returns), with no upper cap on the number of months it can accumulate.
The two returns most businesses deal with monthly are GSTR-1 and GSTR-3B.
GSTR-1 is your sales statement — every invoice you raised, with the buyer's GSTIN, invoice amount, and tax breakdown. This needs to be filed by the 11th of the following month if you're under the QRMP scheme for quarterly filing, or monthly otherwise.
GSTR-3B is your summary return where you declare your total output tax collected, claim your Input Tax Credit, and pay the net GST due. This is due by the 20th of the following month.
The part that confuses most new businesses
Your GSTR-3B ITC claim is linked to your suppliers' GSTR-1 filings. When your supplier files their GSTR-1, your purchases appear in your GSTR-2B automatically. You can only claim ITC for what's in your GSTR-2B.
This means if your supplier is late filing, your ITC is delayed. It's your money, but you have to wait for them to file before you can claim it. This is why supplier filing discipline matters — their late filing costs you cash.
Common first-year mistakes
The most common one is treating GST as a year-end concern. It's not. It's a monthly obligation with monthly deadlines and monthly cash implications. If you've been collecting 18% GST from your customers but not filing and paying regularly, you're accumulating a liability plus late fees plus interest.
The second is not matching purchase invoices against GSTR-2B before claiming ITC. Claiming ITC without a matching GSTR-2B entry is the fastest way to generate a mismatch notice.
The third is mixing input tax credit on exempt and taxable supplies. If any part of your business involves exempt supplies — some exports, certain services — there are specific rules about how you can and can't claim ITC on shared purchases. Get clarity on this early from your CA.
The threshold question
GST registration is mandatory once your aggregate turnover crosses ₹40 lakh (₹20 lakh in some states and for service providers). If you're below the threshold, registration is optional but can still make sense — especially if your customers are GST-registered businesses who want to claim ITC on purchases from you.
If you're selling entirely to end consumers and under the threshold, voluntary registration just adds compliance work without a corresponding benefit. Assess based on who your customers are.
What makes GST manageable
Businesses that handle GST without stress aren't doing anything magical. They file on time every month, they reconcile GSTR-2B against their purchase register before claiming ITC, and they keep their sales records clean enough that GSTR-1 can be filed directly from their accounting software.
It becomes routine once the process is in place. The difficulty isn't the GST itself — it's the first few months of figuring out how your records and your returns connect to each other.
