🧾 Invoice Calculator

GST Invoice Calculator - How to Create a Correct Tax Invoice for India

Getting a GST invoice right is more than just adding numbers - it's a legally binding document that determines your client's ability to claim Input Tax Credit (ITC). An incorrect invoice (wrong GSTIN, wrong GST type, missing mandatory fields) can mean your client is denied the ITC they're entitled to, creating friction, disputes, and delayed payments. This tool generates invoice calculations correctly every time.

CGST + SGST vs IGST - The Most Important Decision on Any Invoice

The most common invoicing mistake in India is applying the wrong GST type - using CGST/SGST when IGST applies, or vice versa. The rule is simple but must be applied consistently:

TDS on Invoices - What Freelancers and Consultants Must Know

TDS (Tax Deducted at Source) is deducted by the payer (your client), not you. It is a prepayment of income tax on the amount you receive. Understanding which section applies and whether your client is required to deduct prevents disputes:

• Section 194J (Professional/Technical Services): 10% TDS. Applies to doctors, engineers, lawyers, accountants, consultants, IT professionals, technical services. Most common section for knowledge workers.
• Section 194C (Contract/Work Payments): 1% for individuals/HUF, 2% for companies. Applies to contractors, labour suppliers, job work. Lower rate but applies to a broad range of work contracts.
• Section 194IB (Rent - Individual to Individual): 5% on rent above ₹50,000/month.
• Section 194I (Rent - Paid by Entities): 10% on plant/machinery, 10% on land/building.

TDS is deducted on the base invoice amount - excluding GST. Your invoice should show the base amount, GST separately, and then "TDS to be deducted by client: ₹X (u/s 194J @10%)" as a deduction from the final payable amount. You receive the net amount; the TDS appears in your Form 26AS as a credit against your income tax liability.

Mandatory Fields on a Valid GST Tax Invoice

A tax invoice without these fields is not legally valid for ITC claims:

• Supplier's GSTIN - Your GST registration number
• Supplier's name, address, and state
• Recipient's GSTIN (for B2B - buyer's GST number)
• Invoice number - Consecutive, unique per financial year
• Invoice date
• Description of goods/services with HSN code (goods) or SAC code (services)
• Quantity and unit of measurement
• Taxable value (after discounts)
• GST rate and amount - CGST + SGST or IGST separately
• Total invoice value
• Place of supply - determines intra-state vs inter-state
• Signature or digital signature

Tax Invoice vs Proforma Invoice - When to Use Each

These two documents serve very different legal purposes and must not be confused:

• Proforma Invoice: A preliminary document before goods/services are delivered. Functions as a quote or advance estimate. Does NOT create a GST liability. Buyer CANNOT claim ITC on a proforma invoice. Used for advance payment requests or to show clients the expected cost.
• Tax Invoice: Raised after goods are delivered or services are rendered. Creates your GST liability for the period. Buyer CAN claim ITC on a tax invoice (if they are GST-registered). This is the document you issue after completing work and expect to be paid against.
• Credit Note: Issued to reduce a previously raised tax invoice (e.g., returns, post-supply discounts, or price revisions). Adjusts both parties' GST liability.