Articles · Running a business in Sri Lanka
How 18% VAT is calculated on a Sri Lankan invoice, with worked examples
Adding VAT to a net price, taking it out of an inclusive price, rounding line by line, mixed baskets with exempt items, and what a tax invoice has to show — with the arithmetic written out.
Value Added Tax in Sri Lanka has been 18% since 1 January 2024. Most invoices that go wrong do not go wrong on the rate; they go wrong on where the 18% is applied, how it is rounded, and what happens when a basket mixes taxable and exempt items. This article writes the arithmetic out, because it is the arithmetic that ends up in a dispute with a customer or a query from the Inland Revenue Department.
It is written for a shop or small business owner, not an accountant. Where the rules depend on your registration or your sector, it says so and points at the Inland Revenue Department rather than guessing.
Who has to charge VAT?
A business must register for VAT once its taxable supplies pass the registration threshold, which at the time of writing is LKR 60 million in any twelve-month period (or LKR 15 million in a quarter). Below the threshold, registration is voluntary. Once registered, you charge VAT on taxable sales, you can claim the VAT you paid on business purchases, and you file returns to the IRD on the schedule the department assigns you. The threshold and the schedule change from time to time; confirm them on the IRD site before relying on this paragraph.
If you are not registered, you do not charge VAT and you must not print "VAT" on your receipts.
How do I add 18% to a price?
Multiply the net price by 0.18 to get the tax, and add it.
| Amount | |
|---|---|
| Net price | LKR 10,000.00 |
| VAT at 18% (10,000 × 0.18) | LKR 1,800.00 |
| Total the customer pays | LKR 11,800.00 |
The shortcut is to multiply by 1.18: 10,000 × 1.18 = 11,800.
My shelf prices already include VAT. How much of the price is tax?
This is where most mistakes happen. The tax is not 18% of the shelf price. The shelf price is 118% of the net price, so the tax is 18/118 of it.
| Amount | |
|---|---|
| Shelf price, VAT inclusive | LKR 11,800.00 |
| VAT inside it (11,800 × 18 ÷ 118) | LKR 1,800.00 |
| Net price (11,800 − 1,800) | LKR 10,000.00 |
The fraction 18/118 is about 0.1525. Taking 18% of 11,800 would give 2,124, which overstates the tax by 324 rupees and understates your sale. On a shop's monthly return that error compounds into a real amount.
Should I round per line or per invoice?
Compute the VAT on each line, round each line to the cent, then add the lines. Do not compute VAT once on the invoice total and then try to allocate it back to lines: the two methods differ by a few cents on some invoices, and the line-by-line method is the one that survives an audit and matches what the customer sees on the receipt.
An example with three items:
| Item | Net | VAT 18% | Line total |
|---|---|---|---|
| Rice 5 kg | 1,390.00 | 250.20 | 1,640.20 |
| Ginger beer 330 ml × 3 | 450.00 | 81.00 | 531.00 |
| Cotton T-shirt | 1,490.00 | 268.20 | 1,758.20 |
| Invoice | 3,330.00 | 599.40 | 3,929.40 |
Check: 3,330 × 0.18 = 599.40. Here the two methods agree; on invoices with many odd-cent lines they can differ by one or two cents, and the line method is the one to keep.
What if some items are exempt or zero-rated?
Some supplies are exempt from VAT and some are zero-rated; the lists are set by law and change with each budget, so take them from the IRD, not from a blog post. What matters for the invoice is mechanical: VAT is calculated per line at that line's rate, and the invoice shows the taxable and non-taxable totals separately.
| Item | Rate | Net | VAT | Line total |
|---|---|---|---|---|
| Taxable item | 18% | 2,000.00 | 360.00 | 2,360.00 |
| Exempt item | exempt | 800.00 | 0.00 | 800.00 |
| Invoice | 2,800.00 | 360.00 | 3,160.00 |
Software that applies one rate to the whole basket cannot produce this invoice correctly. It is one of the first things to test in any till you evaluate.
What does a tax invoice have to show?
A VAT-registered business issues a tax invoice to registered customers, and a simpler receipt to others. The IRD prescribes the particulars; broadly, a tax invoice shows:
- the words "Tax Invoice";
- your name, address and VAT registration number;
- the invoice date and a serial number;
- the customer's name, address and VAT number, for a tax invoice to a registered person;
- a description of the goods or services, quantities and prices;
- the VAT amount shown separately from the net amount, and the total.
Keep copies for the period the law requires; the software should do this for you, unaltered, and be able to reprint any invoice by its serial number.
How does this show up in the books?
For every sale, the net amount is revenue and the VAT is not: it is money you hold on behalf of the IRD, a liability, until you pay it over. The purchase side is the mirror: the VAT you pay to suppliers is a claim against the IRD. The return nets the two. A system that posts each sale as revenue plus a VAT liability, and each purchase as cost plus VAT recoverable, produces the return's figures without anyone re-adding receipts.
In Sevo Biz App, every sale line stores the rate that applied at the moment of sale, the VAT report groups output tax by rate, and the double-entry ledger carries the liability, which is exactly the arithmetic above done by software rather than at month end. Any well-built system should do the same; ask the vendor to show you the per-rate VAT report before you buy.
Frequently asked
Can I show prices without VAT in the shop?
For retail, customers expect the shelf price to be what they pay, so inclusive pricing is the norm and the receipt breaks the VAT out. For business-to-business quotations, net prices plus VAT are usual. Either is fine as long as the invoice itself shows the VAT separately.
What happens if I charged the wrong rate?
Issue a credit note for the wrong invoice and a new invoice at the right rate; do not edit the original. Your books must show what actually happened, in order.
Does VAT apply to services as well as goods?
Yes, unless the specific service is exempt. The arithmetic is identical.
This article explains arithmetic and general requirements as at September 2026. It is not tax advice; thresholds, rates and the exempt list are set by law and change. Confirm your own position with the IRD or your accountant. Webdesigns Lanka builds Sevo Biz App, which does this arithmetic for Sri Lankan shops.