Why Your Buyer’s Accountant Is Rejecting Your Invoices (And How to Fix It)
The 8 GST invoice errors that delay payments — and a checklist to prevent them
Few things are more frustrating than completing a job, sending an invoice, and then waiting — only to hear from your client that their accounts team ‘can’t process it.’ Often, the issue isn’t the payment itself but the invoice format.
For GST-registered buyers, their accountants are strict about invoice quality because every input they feed into GSTR-2A reconciliation has to be verifiable. A bad invoice doesn’t just delay your payment — it creates a compliance problem for your buyer too.
Here are the 8 most common reasons invoices get rejected, and the simple fixes for each.
Error 1: Missing or Wrong GSTIN
What happens: Your invoice either omits your GSTIN entirely, shows an old GSTIN (from a previous registration or amendment), or contains a typo in the 15-digit number.
Why it matters: The buyer’s accountant cannot match your invoice to GSTR-2A without a valid GSTIN. The ITC claim fails.
Fix: Add your GSTIN to your invoice template permanently. Verify it against the GST portal before using. The 15th character is a checksum — a valid GSTIN has a specific pattern: 2 state digits + 10 PAN digits + 1 entity digit + 1 default Z + 1 checksum.
Error 2: CGST and SGST Not Shown Separately
What happens: The invoice shows ‘18% GST: ₹3,600’ as a single line. The buyer’s system expects two separate lines: ‘CGST 9%: ₹1,800’ and ‘SGST 9%: ₹1,800’.
Why it matters: CGST goes to the central government, SGST to the state government. They are legally distinct taxes. Combining them makes the invoice non-compliant.
Fix: Use a billing tool that automatically splits CGST and SGST. Never show a combined ‘GST’ amount for intra-state supplies.
Error 3: Wrong IGST vs CGST/SGST
What happens: You’re in Maharashtra, your client is in Gujarat — an inter-state supply. You charge CGST+SGST instead of IGST.
Why it matters: This is a fundamental GST error. IGST on inter-state, CGST+SGST on intra-state. Wrong application means your client receives the wrong tax credit and your GSTR-1 mismatches their GSTR-2A.
Fix: Check the buyer’s state before raising every invoice. Inter-state = IGST. Same state = CGST+SGST.
Error 4: Invoice Date Outside the Allowed Window
What happens: You completed a service on March 10 but issued the invoice on April 15 — after the financial year end.
Why it matters: For services, the invoice must typically be issued within 30 days of the supply date. A late invoice creates GST liability issues for both parties. Cross-year invoices are even more complex.
Fix: Invoice within 30 days of service completion. For goods, invoice at or before delivery.
Error 5: Incorrect or Missing HSN/SAC Code
What happens: The invoice either omits the HSN/SAC code, uses the wrong one, or uses a generic code that doesn’t match the actual goods/service.
Why it matters: Buyers with turnover above ₹5 crore cannot claim ITC on invoices without valid HSN/SAC codes. GSTR-1 filing also requires HSN/SAC summary.
Fix: Look up the correct HSN code for your goods (customs tariff schedule) or SAC code for your service. Add it to your billing template permanently.
Error 6: Non-Sequential Invoice Numbers
What happens: Invoice numbers jump (INV-101, then INV-105), repeat, or restart mid-year without a new series.
Why it matters: GST auditors look for gaps in invoice sequences. Missing invoice numbers imply unreported income. Buyers’ accountants also flag invoices that don’t follow a clear series.
Fix: Use a single, sequential numbering series within each financial year. If you need to void an invoice, issue a credit note — don’t just skip the number.
Error 7: Place of Supply Not Stated
What happens: The invoice doesn’t show the place of supply — just the billing address.
Why it matters: Place of supply determines the applicable tax type (IGST vs CGST/SGST) and which state receives the tax revenue. It’s a mandatory field under the GST rules.
Fix: Add a ‘Place of Supply’ field to your invoice template. For B2B, it’s generally the buyer’s state. For B2C, it’s the supplier’s state for supplies below ₹2.5 lakh.
Error 8: No Authorised Signature
What happens: The invoice PDF has no signature — either physical or digital — from the supplier’s authorised signatory.
Why it matters: A valid tax invoice must be signed by the authorised signatory of the registered person. An unsigned invoice is technically incomplete under GST rules.
Fix: Add a digital signature image or a printed signature block to your invoice template. For e-invoices, the IRN and QR code serve as the digital authentication.
The Fastest Way to Avoid All 8 Errors
The most reliable solution is a GST bill generator that has all these rules built in — that forces you to enter GSTIN, auto-splits CGST/SGST, applies IGST for inter-state supplies, and maintains invoice sequence automatically.
🔗 Free GST Bill Generator — mybooksai.app — Create error-free GST invoices free — all mandatory fields built in
Quick checklist: Before sending any invoice: ✓ Your GSTIN correct ✓ Buyer GSTIN included (B2B) ✓ CGST/SGST or IGST correctly applied ✓ HSN/SAC code present ✓ Place of supply stated ✓ Invoice date within 30 days ✓ Sequential invoice number ✓ Signed by authorised signatory
About MyBooksAI
MyBooksAI is a free AI-powered cloud accounting platform built for Indian SMEs and emerging market businesses. It includes free tools for GST billing, UPI QR generation, purchase orders, quotations, and proforma invoices — no signup required for the tools. For full accounting automation, visit mybooksai.app.
