GSTR1 and GSTR 3B, from the billing side. The return is downstream of the invoice, and nearly every filing problem is an invoice problem that was invisible at the time.
Why returns fail to reconcile
Almost never because of arithmetic. Nearly always because of a field that was missing when the invoice was raised.
- The customer’s GSTIN was not captured, so a B2B supply sits in B2C.
- The place of supply was wrong, so an inter-state sale was billed as CGST + SGST.
- The HSN was blank, so the HSN summary cannot be produced.
- The invoice series has a gap or a duplicate, because two people billed on two machines.
- A credit note does not reference the invoice it corrects.
None of these can be repaired at filing time without going back to the invoice — and by then the customer already has it.
GSTR-1 and GSTR-3B: how the two have to agree
These two are filed for the same period and describe the same business, which means they have to reconcile — and the department's first check is simply whether they do.
GSTR-1 is the detail: every outward supply, invoice by invoice for B2B. GSTR-3B is the summary: totals for outward supplies, the input credit claimed, and the net tax paid. The outward supply figures in the two should match. Where they do not, the difference is visible without anyone having to look at an invoice, which is why it is the most commonly questioned thing in GST.
The usual causes of a gap are mundane. An invoice entered in one period and reported in the other. A credit note taken into 3B but not declared in GSTR-1. An amendment made in one return and not the other. Or simply two different people compiling the two returns from two different spreadsheets.
The practical defence is that both returns should be produced from the same records rather than compiled separately. If GSTR-1 comes out of your invoice list and 3B is typed from a summary somebody made, a gap is a matter of time.
What Billixo does for return time
- Mandatory fields cannot be skipped. GSTIN, place of supply, HSN and the tax split are captured on the invoice, not reconstructed later.
- Tax split derived, not chosen. Inter-state is IGST because the customer’s state says so, not because someone picked it.
- A consecutive invoice series issued centrally, restarting each financial year — no gaps, no duplicates, whoever is billing.
- GSTR-1 summary of outward supplies, B2B and B2C separated, with the HSN summary.
- GSTR-3B summary of the net position.
- Credit and debit notes that reference the original invoice properly.
- Exports in CSV, Excel and JSON that a practitioner can open without repairing the file.
- Everything scoped to a period, so a month can be closed and looked at again later without ambiguity.
A month-end sequence that works
- On the 1st, stop billing into the closed month. A cut-off that everyone respects removes more problems than any software feature.
- Check the invoice series for the month — no gaps, no duplicates, and the last number continues into the new month.
- Review B2B invoices for a missing or malformed GSTIN. These are the ones that cost your customer credit.
- Review anything billed to another state and confirm it carries IGST.
- Confirm every line has an HSN or SAC.
- Download the GSTR-1 summary and reconcile the total to your own sales figure for the month.
- Reconcile purchases against the downloaded GSTR-2B, and chase suppliers who have not filed.
- Hand the summaries to whoever files, with the reconciliation working file attached.
Late filing, and why it compounds
Late fees and interest are the visible cost. The larger cost is that a late GSTR-1 delays your customers’ input credit, and business customers notice.
The other compounding effect is internal: a month that was not closed properly makes the next month harder to close, because you are now reconciling two. Three months of that and the annual return becomes a project.
Closing on time is mostly about the data being ready on the 1st, which is a billing problem, not a filing one.
What your CA actually wants from you
Not access to your software. A complete, correct outward supply summary in a file they can open, and a purchase list that reconciles to 2B.
The most common complaint from practitioners is not that a client uses the wrong product. It is that the data was never captured — GSTINs missing, place of supply guessed, HSN blank — and no amount of skill at the filing end recovers that.
A billing system that makes those fields unavoidable is worth more to your accountant than one with better reports.
HSN and SAC codes, and how many digits you need
Every line on a tax invoice needs an HSN code for goods or a SAC for services. How many digits depends on your aggregate turnover in the preceding financial year — smaller businesses report fewer digits than larger ones, and B2B and B2C invoices are treated differently.
Because the requirement is tied to turnover and has been tightened in stages, the practical answer is to store the fullest code you can against each product once, and let the software report at the level required. A six-digit code can always be truncated; a two-digit one cannot be expanded.
Billixo keeps the code on the product record and carries it onto every line automatically, and its AI HSN lookup will suggest one from a plain description when you genuinely do not know.
Invoice numbering: one unbroken series per year
The invoice number has to be consecutive, unique within the financial year, and no more than sixteen characters of letters, numbers, slashes and hyphens. Gaps invite questions. Duplicates cause them.
This is the single most common reason a spreadsheet-based billing setup fails an audit: two people billing on two machines, both starting from the last number they remember. A system that issues the number centrally cannot make that mistake.
The series restarts on 1 April, and Billixo restarts it for you rather than waiting to be told.
The AI, and what it is actually for
The useful application of AI to billing is not a chatbot. It is the twenty minutes a day spent retyping things that already exist on paper.
- Scan a supplier bill. Photograph it; the lines, the GSTIN, the tax and the totals come back as a draft you check rather than a form you fill.
- Find the HSN code. Describe the product in plain words and get a code to confirm, instead of scrolling a list of eleven thousand.
- Ask about your own numbers. "What is outstanding over sixty days?" answered from your data, not a manual.
- Write the reminder. A polite, specific chase for an overdue invoice, ready to send on WhatsApp.
Nothing is sent anywhere until you ask for it, and the platform runs on whichever model it has been configured with — including one hosted on your own server.
Who this actually suits
It fits a business that raises between a handful and a few hundred invoices a month and would rather not think about GST between the 10th and the 20th: traders, distributors, retail counters, workshops, agencies, consultants, contractors and manufacturers who sell on invoice.
It fits less well if you need deep manufacturing costing, multi-currency consolidation, or payroll — those are different products, and pretending otherwise wastes your evaluation time.
If you are not sure which side of that line you fall on, the free plan answers it in an afternoon at no cost. Start free now.
Free, and what it costs you instead
Free software usually costs you something that is not money: your data held hostage, an export that does not work, ads inside your invoice, or a "free" tier so narrow it is a demo with a login screen.
The line here is drawn differently. Export works on the free plan — CSV, Excel and JSON — because data you cannot get out is not data you own. The invoice is a real compliant invoice, not a sample. The limits are on volume and on the conveniences, not on whether the thing works.
Start free now. If it does not suit you, take your data with you.
Where your data lives
On the server this platform is installed on. Every record carries a company identifier and every query is scoped to the signed-in account at the framework level, so one business cannot read another’s data by any route, including a crafted one.
Sign-in is rate limited, sessions can be restricted to one device per user, and passwords are stored hashed. Exports are available on every plan, free included: if you ever want to leave, your data leaves with you.
Frequently asked questions
How far back can I fix a mistake?
Corrections are made by credit or debit note referencing the original invoice, and the adjustment has to be declared within the statutory window — broadly, by the relevant return of the following financial year or the annual return, whichever is earlier. Past that the commercial correction stands but the tax adjustment does not.
Does Billixo file my GST returns?
No — it prepares them. GSTR-1 and GSTR-3B summaries are produced from your invoices and exported for filing on the portal or by your practitioner. The filing and the responsibility for it stay with you, which is where they legally sit.
Is the GST return export available on the free plan?
No. The Free plan produces fully compliant invoices, but GSTR-1 and GSTR-3B export is a paid feature. Every new account gets the full paid feature set for its first 14 days, so you can see the export before deciding.
Is my data shared with anyone?
No. It sits in this installation, scoped to your company. AI requests only happen when you explicitly ask for one, and nothing is sent anywhere otherwise.
Is it really free?
Yes. The Free plan is ₹0, needs no card and has no expiry. It has volume limits and leaves out the paid conveniences — watermark-free PDFs, GST return exports, the AI features, extra logins — but the invoices it produces are real GST invoices, and you can export your data from it whenever you like.
Start free, decide later
You do not have to choose a plan to begin. Start on Free, use it for as long as it suits you, and upgrade only when a limit actually gets in your way — never automatically, and never because a countdown ran out.
Open the software demo → — or create the free account from the same page.
Read the full details → on the home page, including pricing and the AI features.
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