Do I Need an ABN to Start a Business? A Country-by-Country Answer

You do not need an ABN merely to begin: an ABN is tied to running a business or other enterprise in Australia, while the United Kingdom lets a sole trader start trading without registering first. Before relying on either system, check the separate VAT/GST rules: the general registration thresholds cited below are A$75,000 in Australia, £90,000 in the UK, and more than S$1 million in Singapore, each checked for this page on 2026-10-01.

Which business ID or tax registration is relevant before the first sale?

Country	What applies before or when the business starts	Main ID or registration identified in the official guidance
Australia	Not everyone needs an ABN; it is for a person running a business or other enterprise. An ABN is also required before GST registration.	Australian Business Number (ABN)
United Kingdom	A sole trader can start trading without registering. Self Assessment becomes compulsory if annual trading income exceeds £1,000.	Self Assessment registration and, once issued, a Unique Taxpayer Reference (UTR)
United States	The federal tax ID is an Employer Identification Number (EIN), but the IRS list does not establish that every sole proprietor must obtain one.	EIN for the federal circumstances listed by the IRS
Singapore	The official material provided for this page does not state that a separate business ID must be obtained before the first sale.	GST registration is addressed separately
Hong Kong	A person carrying on a business in Hong Kong must apply for business registration within one month after commencement.	Business Registration Number (BRN), adopted as the Unique Business Identifier

These rules come from the ATO, HM Revenue & Customs, IRS, IRAS, and Hong Kong IRD material checked for this page on 2026-10-01.

Do I need an ABN to start a business in Australia?

Not automatically. The official position is that an ABN is intended for someone running a business or other enterprise, and it is required before registering for GST.

An ABN identifies the business when it deals with government, customers, and other businesses. It can also be used when ordering and invoicing, to avoid PAYG tax on payments received, and to claim GST credits. It does not replace the tax file number.

These figures and definitions come from the Australian Taxation Office and business.gov.au material checked for this page on 2026-10-01.

When does GST registration become compulsory?

The ordinary threshold is A$75,000 or more in GST turnover. A non-profit organisation’s threshold is A$150,000 or more, while taxi or limousine travel must register regardless of turnover.

GST turnover is tested under either:

the current period: the current month plus the previous 11 months; or
the projected period: the current month plus the next 11 months.

For a new Australian business, registration is required within 21 days after becoming aware that turnover will exceed the applicable threshold. An overseas business selling imported services, digital products, or low-value goods to Australian consumers must also register once its GST turnover reaches A$75,000 or more.

A non-resident may need to register depending on the business activities. Failure to register when required can result in GST due on earlier sales, plus penalties and interest.

Source: Australian Taxation Office and business.gov.au; checked for this page on 2026-10-01.

Is voluntary GST registration available in Australia?

Yes. A business below the usual threshold may choose to register. Once registered, it generally must include GST in most prices, claim eligible GST credits, and lodge activity statements.

If registration is not compulsory, voluntary registration generally commits the business to remain registered for at least 12 months. Source: Australian Taxation Office; checked for this page on 2026-10-01.

Can a UK sole trader trade before registering?

Yes. HM Revenue & Customs says a sole trader can start trading straight away without registering. That does not mean every tax obligation waits until later.

Self Assessment registration is compulsory when the sole trader earns more than £1,000 in a tax year, running from 6 April to 5 April. Registration may happen earlier. HMRC issues a UTR after registration, but a typical delivery time is not stated on the official page captured for this article.

Source: HM Revenue & Customs; checked for this page on 2026-10-01.

When does a UK business become liable for VAT?

The ordinary VAT threshold is triggered if taxable turnover:

exceeds £90,000 over the last 12 months; or
is expected to exceed £90,000 within the next 30 days.

Registration is due within 30 days of the end of the month in which the threshold was exceeded. The effective registration date is normally the first day of the second month after exceeding it.

Registration below the threshold is voluntary. A business that sells only VAT-exempt or out-of-scope goods and services does not have to register. Where most taxable supplies are zero-rated, the business may seek an exemption from registration, but it must obtain HMRC permission.

Source: HM Revenue & Customs; checked for this page on 2026-10-01.

Can a business based outside the UK register for VAT?

Eligibility is not limited to UK-established businesses. HMRC states that a business based outside the UK which supplies goods or services to the UK must register for VAT regardless of turnover.

That is a registration rule, not a general promise that every foreign founder will qualify for or receive every UK business status. Source: HM Revenue & Customs; checked for this page on 2026-10-01.

Does a US one-person business always need an EIN?

No blanket answer can be drawn from the captured federal page. The IRS lists specific situations in which an EIN is needed, including where the business has employees, will pay employment or excise taxes, or withholds tax on income paid to a non-resident alien.

An EIN is also used to operate specified entities, including partnerships, LLCs, and corporations. Those entities should be formed with the relevant state before applying to the IRS.

A business that does not need an EIN for federal tax purposes may request one for banking or state-tax purposes. Whether a particular sole proprietor is exempt is not stated on the official page in those exact terms, so the activity, entity type, taxes, employees, and banking or state requirements must be checked separately.

Source: Internal Revenue Service; checked for this page on 2026-10-01.

When does Singapore require GST registration?

IRAS requires GST registration if taxable turnover is:

more than S$1 million at the end of the calendar year; or
expected to be more than S$1 million in the next 12 months.

Under the retrospective test, the application window is 1 January to 30 January of the following year, with registration on 1 March. Under the prospective test, the business must apply within 30 days after the forecast date. For liability arising on or after 1 July 2025, registration takes effect two months from that forecast date.

A business below the threshold may register voluntarily after careful consideration. It may apply for an exemption where taxable turnover is derived wholly or mainly from zero-rated supplies.

An overseas supplier of services or imported low-value goods to non-GST-registered individuals and businesses in Singapore may fall within the overseas vendor registration regime. How a particular foreigner applies, and whether a Singapore entity is required, is not stated on the official page captured for this article.

Source: Inland Revenue Authority of Singapore; checked for this page on 2026-10-01.

Must a one-person business register in Hong Kong?

Yes, if the activity is a business in Hong Kong. A sole proprietorship, partnership, non-Hong Kong company, or branch must apply within one month after commencement. Online businesses can also fall within the registration requirement.

A person who is merely holding an office or employment does not have to register on that basis. Business registration is not a licence to trade.

To apply, the business must complete the prescribed form, pay the registration fee and levy, and provide proof of identity. A non-resident individual can provide a copy of a passport or identity card issued by the relevant government authority. A non-resident sole proprietor must also prove that the Hong Kong business has actually commenced.

The current fee and levy amounts are not stated on the official page text captured for this article. They should be checked against the IRD fee and levy table. Late registration can lead to back-year payments, a fine of $5,000, and imprisonment for 1 year.

Source: Hong Kong Inland Revenue Department; checked for this page on 2026-10-01.

Does the Hong Kong BRN also identify the business?

Yes. Hong Kong IRD adopted the Business Registration Number assigned by its Business Registration Office as the Unique Business Identifier for companies and entities.

The captured IRD business-registration pages do not state whether a separate VAT or GST registration is required. Source: Hong Kong Inland Revenue Department; checked for this page on 2026-10-01.

Frequently asked questions

Do I need an ABN to start trading?

An ABN is not automatically required merely to start. In Australia, it is associated with running a business or enterprise and must be obtained before GST registration. UK sole traders, by contrast, can start trading without first registering with HMRC.

Does the first sale automatically trigger VAT or GST registration?

No single first-sale rule applies across all five places. The countries use different turnover tests, activity-based rules, and exceptions, so the expected and past turnover must be monitored from the start.

Can a foreigner obtain an Australian ABN?

The captured guidance does not give a separate foreigner-specific ABN procedure. For GST, the ATO states that a non-resident may have to register depending on the business activities.

Can a foreign business register for UK VAT?

HMRC states that a business based outside the UK which supplies goods or services to the UK must register regardless of taxable turnover. The relevant supply must fall within the rule; this does not remove the need to examine the specific transaction.

What number identifies a sole proprietor in each country?

The identifiers are not interchangeable: Australia uses an ABN where the eligibility conditions are met; the UK issues a UTR after Self Assessment registration; the United States uses an EIN in the circumstances listed by the IRS; Singapore’s material addresses GST registration; and Hong Kong issues a BRN, also adopted as the Unique Business Identifier.