How to Add GST to Your Invoice

If you are a US-based freelancer or small business owner who has just signed a client in Canada, Australia, India, or the UK, you have probably encountered a confusing acronym: GST. Suddenly your client is asking for a GST number, or asking you to add GST to your invoice, and you have no idea whether you need to charge it or how to format it.

This guide demystifies GST for US sellers. You will learn what GST is, when (and whether) you need to add it to your invoice, how to format a GST-compliant invoice for international clients, how to handle reverse-charge situations, and how to avoid the most common mistakes that cause client AP teams to bounce your invoice. By the end you will be able to issue a GST-aware invoice in five minutes that satisfies foreign tax authorities without overcharging your client.

What GST Is and Who Charges It

GST stands for Goods and Services Tax. It is a value-added tax used in roughly 170 countries worldwide, including Canada (5 percent federal GST, plus provincial HST or PST), Australia (10 percent), India (5, 12, 18, or 28 percent depending on category), Singapore (9 percent in 2026), New Zealand (15 percent), and the UK (where it is called VAT at 20 percent standard rate). The US does not have a GST; we use a patchwork of state and local sales taxes instead.

GST is collected by the seller, remitted to the foreign tax authority, and ultimately borne by the end consumer. For US businesses selling to clients in GST countries, the question is not 'do they have GST' (they do) but 'am I required to register, collect, and remit it.'

The answer for most US freelancers and small businesses: usually no, but there are important exceptions. If you sell digital services (consulting, design, software, content) to a business in a GST country, the buyer is typically required to self-assess and remit GST under a 'reverse charge' mechanism. You as the seller do not register or charge GST. You simply issue a clean invoice with no GST line and a note explaining that reverse-charge applies. If you sell to consumers (not businesses) in a GST country, registration thresholds may force you to register and collect. Australia, the EU, and the UK all have low-revenue thresholds for digital service sellers ($75,000 AUD or 10,000 EUR in the EU one-stop shop, for example).

If you sell physical goods that ship into a GST country, the rules vary by country and shipment value but generally involve customs duties, import GST, and potentially a deemed-seller registration through a marketplace like Amazon or eBay. Consult a cross-border tax specialist for goods.

When You Need a GST Number

A GST number is a registration with a foreign country's tax authority that allows you to legally collect and remit GST on transactions in that country. You only need one if your sales meet the country's registration threshold or if your business model requires it.

Canada: registration is mandatory if you have $30,000 CAD or more in revenue from Canadian customers in a 12-month period. Below that threshold, you are a 'small supplier' and do not need to register. Registration is voluntary if you want to claim input tax credits on Canadian expenses.

Australia: registration is mandatory at $75,000 AUD in annual revenue from Australian customers. Below that, registration is voluntary.

UK: VAT registration threshold is 85,000 GBP in annual UK revenue. Below that, registration is voluntary.

EU: registration threshold varies by country and product type. The EU one-stop shop (OSS and IOSS) lets non-EU sellers register in one EU member state and remit VAT for all EU customers. The threshold for digital services is 10,000 EUR per year across all EU customers.

India: registration threshold for non-resident service providers is generally zero for taxable supplies, but most B2B service exports trigger reverse charge with no seller-side registration.

If your client asks for your GST number and you do not have one (because you are below the threshold or because reverse charge applies), simply state that on the invoice: 'Seller is not registered for GST/HST/VAT. Reverse charge applies to this invoice under section [X] of [country] tax law.' This is the standard response and satisfies nearly all client AP teams.

How to Format a GST-Compliant Invoice

If you do need to charge GST, format the invoice carefully. Foreign tax authorities have specific requirements that differ from a US sales tax invoice.

Required elements for a GST-compliant invoice typically include: your business name and full address; your GST/HST/VAT registration number, prominently displayed; the client's business name and address; the client's GST number if they are also registered; a unique sequential invoice number; the issue date and the supply date; a clear description of goods or services provided; the price excluding GST (the 'net' amount); the GST rate applied; the GST amount in the foreign currency; and the total including GST.

For a Canadian invoice example: 'Subtotal: $1,000 CAD. GST (5 percent): $50 CAD. Total: $1,050 CAD. GST number: 123456789RT0001.'

For an Australian invoice: 'Subtotal: $1,000 AUD. GST (10 percent): $100 AUD. Total: $1,100 AUD. ABN: 12 345 678 901.'

For a UK VAT invoice: 'Net: 1,000 GBP. VAT (20 percent): 200 GBP. Total: 1,200 GBP. VAT registration: GB123456789.'

Currency matters. Issue the invoice in the local currency of the GST country whenever possible. Some clients will accept USD invoices with a GST line, but it complicates their reporting and may trigger an FX conversion that they pass back to you. When in doubt, ask the client's AP team which currency they prefer.

The free invoice generator at /free-tools/invoice-generator supports multi-currency and tax-line formats designed for GST-compliant invoices.

Reverse Charge: The Most Common Scenario for US Sellers

For most US freelancers selling consulting, design, software, or content services to business clients in GST countries, the reverse-charge mechanism is the answer. It is simpler than registering for GST and is the legally correct treatment for cross-border B2B services in most cases.

Under reverse charge, you issue an invoice with no GST line. The buyer in the foreign country self-assesses the GST on their own tax return, both reporting it as input GST (which they reclaim) and output GST (which they remit), netting to zero. From their perspective, the GST is a paperwork exercise, not a cash cost. From your perspective, you issue a normal invoice with a small note.

The note should appear clearly on the invoice. Standard language varies by country but the general format is: 'This supply is subject to reverse charge. Buyer is responsible for self-assessing applicable GST/VAT.' For UK clients: 'Reverse charge: customer to account for VAT under article 196 of Council Directive 2006/112/EC.' For Australian clients: 'GST does not apply to this supply. Recipient is responsible for GST under the reverse charge rules.' For Canadian clients: 'GST/HST not applicable. Recipient may self-assess under Section 218 of the Excise Tax Act.'

The specific legal references reassure foreign AP teams and accountants that you understand the rules. They are not strictly required by US law but dramatically reduce questions and invoice bounces.

If your client questions reverse charge or asks you to register and collect anyway, point them to their accountant. Often a non-expert AP clerk is just doing what they have always done, and a 5-minute call with the accountant clears it up.

What to Do if You Are Required to Register

If you exceed a country's registration threshold or sell to consumers in a GST country, you may need to register. The process varies by country but generally follows these steps.

Step one: register online with the foreign tax authority. Canada Revenue Agency (CRA), Australian Taxation Office (ATO), UK HM Revenue and Customs (HMRC), and EU OSS portals all have non-resident registration processes. You will need your US business details, an EIN, banking info for any refunds, and proof of identity.

Step two: charge GST on relevant sales. Add the appropriate GST line to invoices for customers in that country. Use the right rate (Canada 5 percent federal plus provincial; Australia 10 percent; UK 20 percent standard, 5 percent reduced, 0 percent zero-rated).

Step three: file periodic returns. Canada is quarterly or annual depending on revenue. Australia is quarterly. UK is quarterly. EU OSS is quarterly. Most filings are online and take 30 minutes if your bookkeeping is clean.

Step four: remit collected GST to the foreign tax authority. They will provide bank details for international wire transfers, typically in their local currency. Set aside collected GST in a separate bank account so you do not accidentally spend it.

Most US freelancers below the threshold should not register voluntarily. The compliance burden (returns, foreign accounting, currency conversion) outweighs any benefit unless you have significant input GST to reclaim from local expenses, which is unusual for US-based sellers.

If you do reach the threshold, hire a cross-border accountant for at least the first year. A specialist will save you days of confusion and prevent expensive registration errors. Look for CPAs with experience in either US-Canada or US-EU/UK cross-border work. Hourly fees of $200 to $400 are normal and well worth it.

Common GST Invoice Mistakes

Mistake one: charging GST when you should not. Many US freelancers panic and add a 'GST' line to invoices for Canadian or Australian clients without being registered. This is illegal: you are collecting tax you cannot remit. Always confirm registration status before adding GST.

Mistake two: skipping the reverse charge note. If reverse charge applies and you do not state it, the client may withhold a percentage of payment to cover what they assume is GST. State reverse charge explicitly on the invoice.

Mistake three: using the wrong rate. Canada has both federal GST (5 percent) and provincial HST (varies from 13 to 15 percent in HST provinces) or PST (varies, separate from GST in non-HST provinces). Confirm which applies based on the client's province. Australia is a flat 10 percent. UK has multiple rates depending on the goods or service category.

Mistake four: using the wrong currency. Issue invoices in the client's local currency when possible. A USD invoice with a CAD GST line is confusing and may bounce.

Mistake five: missing the registration number. If you are registered, your number must appear on every invoice. Without it, the client cannot claim input GST and may bounce the invoice.

Mistake six: forgetting that your client may withhold tax. Some countries require buyers to withhold a portion of payment to US contractors under tax treaty rules. Form W-8BEN-E and W-8BEN are used to claim treaty benefits and reduce withholding. Provide these forms proactively.

Ready to issue clean, international-friendly invoices? Try the free generator at /free-tools/invoice-generator, which supports multi-currency invoices and pre-loaded tax templates for major GST countries. For automatic FX rate updates, GST-compliant templates by country, and reverse charge notes, upgrade to a paid Eonebill.ai plan at /pricing. International billing should be the easy part, not the scary part.

The regulatory environment for cross-border tax is shifting fast. The OECD's Pillar One and Pillar Two initiatives, EU VAT reform, and various national digital services taxes (DST) are changing how international tax applies to digital services. As of 2026, several countries have introduced or proposed taxes targeting non-resident digital service providers, including India's Equalisation Levy, France and UK Digital Services Taxes, and Canada's proposed DST. Most of these target large multinationals (over $750 million or $1 billion in global revenue), so small US freelancers are not directly impacted. But the regulatory direction is toward more cross-border tax obligations, not fewer.

Stay informed by following one or two reliable resources. The IRS International Taxpayers page, the OECD tax newsroom, and the Tax Foundation's international tax reports are the best free sources for US-based small business owners. For region-specific updates, the Canada Revenue Agency, Australian Taxation Office, and HM Revenue and Customs all publish accessible non-resident guidance. Subscribe to one cross-border tax newsletter (Avalara and TaxJar both publish good ones) for changes that affect your specific markets.

Finally, when in doubt, consult a CPA. The cost of a 1-hour consultation ($200 to $400 typically) is far less than the cost of a misfiled tax return or an unexpected withholding event. Look for CPAs who specifically advertise cross-border or international tax experience. A specialist will resolve most GST and VAT questions in 30 minutes that would take you 3 hours of reading to half-understand. Spend on the specialist; save your time for the work that grows your business.