GST invoice workflow (India)
Incorrect GST on invoices creates payment delays, rejected input tax credit for your clients, and compliance headaches during filing. Whether you are a freelancer, agency, or small SaaS vendor, the workflow is the same: determine the transaction type, calculate tax splits accurately, document mandatory fields, and issue a PDF your client's accounts team can process without back-and-forth. This guide connects the GST Calculator and Invoice Generator into one repeatable billing process.
Step 1: Confirm registration and place of supply
Only GST-registered businesses charge GST on taxable supplies. Know your GSTIN, legal business name, and registered address — they must appear on every invoice. Place of supply determines whether you charge CGST+SGST (intrastate) or IGST (interstate). If you are in Karnataka and your client is in Maharashtra, IGST applies on a B2B service; same-state clients get CGST and SGST at half the rate each.
For export of services where LUT/zero-rating applies, follow your CA's guidance — this guide covers standard domestic taxable invoices. When in doubt, confirm SAC/HSN codes for your service category before your first bill of the quarter.
Step 2: Calculate amounts with the GST Calculator
Open the GST Calculator and enter your base fee. Toggle between tax-exclusive and tax-inclusive modes depending on how you quoted the client. If you said "₹50,000 plus GST," start exclusive; if you said "₹59,000 all inclusive," start inclusive and back out the base.
Select the correct rate — 18% is common for IT services, 12% and 5% apply to specific goods and categories. The calculator splits CGST/SGST for intrastate or shows IGST for interstate. Write down all four numbers: taxable value, CGST, SGST or IGST, and invoice total. These feed directly into your invoice line items without rounding drift from mental math.
Step 3: Gather mandatory invoice fields
Indian tax invoices require specific fields: consecutive invoice number, date, supplier and recipient GSTIN (for B2B), place of supply, HSN/SAC code, taxable value, tax rate, tax amount, and total. For unregistered recipients (B2C), GSTIN is omitted but other fields remain.
Match the recipient legal name to their GST registration exactly — "Acme Pvt Ltd" versus "Acme Private Limited" can block their ITC claim. For retainers, reference the PO number or SOW clause in the description field so their AP team routes payment correctly.
Step 4: Generate the invoice PDF
Use the Invoice Generator to assemble line items, quantities, rates, and the tax breakdown from Step 2. Add payment terms (Net 15, Net 30), UPI ID or bank details, and a note on late payment interest if your contract specifies it. Preview the PDF before sending — truncated descriptions and wrong decimal places are the top reasons invoices bounce back.
Email the PDF from your business domain, not a personal Gmail address, and keep a copy in a folder named YYYY-MM for GSTR-1 reconciliation. Filename convention: INV-2026-014-Acme.pdf.
Step 5: Handle revisions and credit notes
If you overbilled tax or used the wrong GSTIN, do not edit the original PDF informally. Issue a credit note with its own serial number referencing the original invoice, then reissue a corrected invoice. Track the sequence in a spreadsheet: invoice number, client, taxable value, CGST/SGST/IGST, payment date, and GSTR-1 filing period.
When clients request pro-forma invoices before payment, mark them clearly as "Pro-forma — not a tax invoice" so they are not used for ITC claims until you issue the final numbered document on payment confirmation.
Step 6: Monthly reconciliation habit
Before filing GSTR-1, sum all invoices issued in the period and compare totals to the GST Calculator outputs you saved. Mismatches usually come from rounding per line versus rounding on the total — pick one method and use it consistently. Cross-check received payments against invoice totals; partial payments still reference the full invoice until a credit note closes it.
This workflow — place of supply, calculator, mandatory fields, PDF generation, reconciliation — keeps billing tight enough for clients to pay fast and clean enough for your CA to file without rework. Pair GST Calculator with Invoice Generator every billing cycle until the steps become muscle memory.