How to Use This Invoice Calculator
This free online invoice calculator is designed for anyone who needs to compute invoice totals with GST or VAT quickly and accurately. It works for Indian GST invoices, UK VAT, EU VAT, US sales tax, and any other percentage-based tax system. Here is how to use it in three steps:
- Select your tax rate — choose from the preset buttons (GST 5%, 12%, 18%, 28%, UK VAT 20%, Germany VAT 19%) or enter a custom rate. If you are doing an inter-state transaction in India, enable the IGST toggle to show the full integrated rate instead of splitting CGST and SGST.
- Add your invoice items — enter a description, quantity, and unit price for each product or service. Click "Add another item" to include as many line items as needed. The calculator supports unlimited items.
- Click "Calculate Invoice" — instantly see the subtotal, CGST/SGST breakdown (or IGST for inter-state), total tax amount, and grand total. Use the Copy button to copy the summary to your clipboard.
How GST is Calculated on an Invoice — With Examples
GST (Goods and Services Tax) is calculated as a percentage of the taxable value of goods or services. The formula is straightforward:
GST Amount = (Item Value × GST Rate) ÷ 100
Invoice Total = Item Value + GST Amount
Example 1: Single item at 18% GST
| Item: Web Design Service | ₹10,000 |
| CGST @ 9% | ₹900 |
| SGST @ 9% | ₹900 |
| Invoice Total | ₹11,800 |
Example 2: Three items at 12% GST
| Item | Net | Tax | Gross |
|---|---|---|---|
| Logo Design (×1 @ ₹5,000) | ₹5,000 | ₹600 | ₹5,600 |
| Social Media Posts (×10 @ ₹200) | ₹2,000 | ₹240 | ₹2,240 |
| Monthly Retainer (×1 @ ₹8,000) | ₹8,000 | ₹960 | ₹8,960 |
| Total | ₹15,000 | ₹1,800 | ₹16,800 |
CGST = ₹900 (6%) · SGST = ₹900 (6%) · Total GST = ₹1,800 (12%)
GST Invoice Requirements in India
Under the GST Act, registered businesses are required to issue a tax invoice for every taxable supply. A valid GST invoice must contain the following mandatory fields:
Supplier Details
Name, address, and GSTIN of the seller
Invoice Number & Date
Consecutive, unique invoice number and date of issue
Buyer Details
Name, address, and GSTIN of recipient (for B2B)
Place of Supply
State name and code — determines CGST/SGST vs IGST
HSN/SAC Code
Harmonized code for goods (HSN) or services (SAC)
Taxable Value
The price before applying GST
GST Rate & Amount
Rate applied and CGST, SGST or IGST amounts separately
Invoice Total
Total amount payable including all taxes
CGST vs SGST vs IGST — Which Applies to Your Invoice?
The type of GST shown on your invoice depends on whether the transaction is intra-state (within the same state) or inter-state (across different states):
CGST + SGST
Seller and buyer are in the same state. GST is split equally — half goes to Centre, half to State.
18% GST = 9% CGST + 9% SGSTIGST
Seller and buyer are in different states. Full GST collected by Centre, then distributed to destination state.
18% GST = 18% IGSTUTGST
Applies in Union Territories like Delhi, Chandigarh, Lakshadweep instead of SGST.
18% GST = 9% CGST + 9% UTGSTQuick rule: If your client's billing address is in the same state as yours — use CGST + SGST. If they're in a different state — use IGST. Use the toggle in the calculator above to switch between the two.
Who Uses This Invoice Calculator?
Freelancers
Calculate client invoices with 18% GST on services in seconds
Small Businesses
Generate accurate tax amounts for B2B invoices
eCommerce Sellers
Compute GST on product sales across India
Accountants
Quick-verify invoice totals and tax breakdowns
Design Agencies
Bill clients for creative services with correct GST
UK/EU Businesses
Calculate VAT invoices for 20% UK or 19% EU rates
Contractors
Add GST 12% or 18% to construction service invoices
Educators
Check if educational services are GST exempt (0%) or taxable
How to use and formula
How to calculate tax on an invoice
For each line: line total = quantity × unit price. Tax = subtotal × rate ÷ 100.
- Add line items with description, quantity, and unit price.
- Select GST, VAT, or custom rate.
- Toggle IGST for inter-state India supply.
- Copy or download the breakdown for your invoice.
Line total = quantity × price
Tax = subtotal × (rate ÷ 100)
Grand total = subtotal + tax
₹10,000 subtotal at 18% GST = ₹1,800 tax, ₹11,800 total.
Why invoice-level tax calculation matters
Business invoices rarely use a single tax rate on one subtotal. Each line may have a different GST slab, sales tax jurisdiction, or exempt status. Rounding per line versus per invoice affects remitted tax by cents that compound across thousands of transactions. Accurate line-by-line tax prevents under-collection, customer disputes, and audit adjustments.
This invoice calculator supports multiple lines with quantity, unit price, and tax rate per row. It sums net, tax, and gross for quotes, pro forma invoices, and sanity checks before you export to accounting software. It does not generate legally formatted PDF invoices with mandatory fields — those depend on country (GSTIN on Indian invoices, seller tax ID on US invoices, etc.).
Multi-line tax math and rounding
Per line: Line net = quantity × unit price; Line tax = line net × (rate ÷ 100); Line total = line net + line tax. Invoice totals sum all lines. Some jurisdictions require tax rounded to the nearest cent per line; others allow invoice-level tax on the sum of net amounts. Pick one method and stay consistent with your ERP and return filings.
Discounts can apply before or after tax depending on policy and law — this tool applies rates to line nets you enter. Document whether prices are tax-inclusive or exclusive on the face of the invoice to avoid reverse-calculation errors by recipients.
GST invoices in India
Tax invoices under GST must show supplier and recipient GSTIN (when registered), HSN/SAC codes, taxable value, CGST/SGST or IGST amounts, and place of supply. B2B invoices need more detail than B2C. E-invoicing and e-way bills apply above turnover thresholds notified by the government.
Use separate lines for items at 5%, 12%, and 18% rather than blending rates. Export invoices may show zero-rated supplies with LUT references. Verify format on cbic-gst.gov.in; this calculator handles arithmetic only.
US sales tax on invoices
US sellers charge sales tax based on ship-to destination for remote sales where nexus exists. Invoices should show jurisdiction, rate, and tax amount or state that tax is included. Exempt sales need exemption certificate numbers on file, not just zero tax on the invoice.
Marketplace facilitators may issue invoices on behalf of sellers — confirm who is the vendor of record. Combine this tool with state-specific rate lookups for address-level accuracy; average state rates are insufficient for filing.
VAT invoices in the UK and EU
VAT invoices require seller VAT number, rate per supply, net and VAT per line, and total gross. Reverse charge B2B cross-border services show customer VAT accountability on the invoice text. Mixed supplies at standard, reduced, and zero rates need clear line separation.
For UK Making Tax Digital, digital links between records matter — manual re-keying from this calculator into returns without audit trail may not comply. Use results as a check against your MTD software.
Invoice best practices
Number invoices sequentially, show payment terms and due date, and match currency symbols to the transaction. Archive PDFs with the tax rate snapshot used at time of sale — rates change mid-year in many states and countries.
Reconcile monthly: sum of invoice tax should tie to sales tax return or GST return within rounding tolerance. For large catalogs, import CSV into this calculator's line model conceptually or use API-enabled tax engines for automation at scale.
Common mistakes to avoid
Mixing 5% and 18% lines without grouping
GST law expects rate-wise totals. Calculate separate subtotals when slabs differ.
Using IGST on intra-state B2B invoices
Same-state supply should show CGST and SGST, not IGST.
Forgetting tax-inclusive vs exclusive pricing
Confirm whether unit prices include tax before using add vs remove mode on other calculators.
Skipping mandatory invoice fields for compliance
GSTIN, HSN, place of supply, and invoice serial rules are not generated by this tool.
Official source and review note
Rates and rules on this page were last reviewed in May 2026 against CBIC / HMRC / IRS (by region). Use the linked authority for filing, registrations, or address-specific compliance.
Build compliant invoice totals
Use this calculator for quotes and draft invoices. Add GSTIN, HSN/SAC, and place-of-supply fields required by law before sending to clients.