Singapore KDP authors: the 9% GST on your Amazon ads

Short answer: without a GST number, you pay 9% on top of every dollar you spend on Amazon ads, and you never get it back. A Singapore KDP author can register for GST voluntarily, far below the S$1 million threshold, and stop paying it. The catch is real: at least 2 years of registration, e-invoicing through InvoiceNow, and GST returns. With S$1,000 of ads a month, the government keeps S$1,080 a year that could stay with you.

For Singapore KDP authors, Merch on Demand designers and small sellers, from the Inland Revenue Authority of Singapore (IRAS) and Amazon Ads' own pages, checked in October 2026. This is information, not tax advice: confirm your case with a tax adviser.

Work out what you lose with our free calculator

How much you lose each year

Singapore GST is 9%. Without a GST number, it is a pure cost on your ads:

Why Amazon charges you 9%

Singapore taxes services bought from abroad by anyone without a GST number. IRAS: "If you are not GST-registered and buy remote services from a GST-registered overseas provider, you must pay GST at the prevailing rate of 9%."

Which Amazon company bills you depends on the marketplace your ads run on:

• amazon.com and the other foreign marketplaces: an Amazon company outside Singapore (Amazon Advertising LLC for amazon.com, for example). Amazon Ads' tax guide says it charges GST when the advertiser "has not provided Amazon with a valid VAT/GST registration number" and "is established in a country that has introduced ESS or remote services rules". Singapore has such rules.
• amazon.sg: Amazon Asia-Pacific Holdings Private Limited, a Singapore company.

Check the Tax line at the bottom of your Amazon Ads invoice: it shows what you paid.

Can a KDP author register for GST?

Yes. Below S$1 million you are not forced to, but you can. IRAS: "You may apply to be GST-registered on a voluntary basis even if it is not compulsory for you to register for GST", if, among other cases, "Your business makes taxable supplies".

Your KDP royalties are what make it pay:

• What you sell Amazon is a right. Under the KDP agreement, you grant Amazon a "nonexclusive, irrevocable, right and license to print" and distribute your book. For GST, granting a right is a supply of services, and your royalties are its price.
• You sell it to Amazon companies outside Singapore. The KDP agreement pays royalties through "the Amazon party that made the sale (or whose affiliate made the sale)", such as Amazon.com Services LLC.
• So your royalties are zero-rated. Section 21(3)(j) of the GST Act zero-rates services "provided contractually to an overseas person" and directly benefiting "an overseas person who is outside Singapore when the services are performed". That is exactly your case: you charge 0% on them.
• Zero-rated sales keep your right to claim. IRAS: "You may benefit from GST registration because you may be able to claim the GST incurred on your purchases", with an example of a business that makes only zero-rated supplies.

The KDP agreement also names a Singapore company, Amazon Asia-Pacific Holdings Private Limited: a royalty it paid would not come from an overseas person. IRAS has never ruled on KDP royalties as such: if you want that in writing before you register, ask it for an advance ruling on your case.

What changes once you are registered

1. Register for GST with IRAS, after the conditions below.
2. Add your GST number to Amazon Ads. As a KDP author: Administration, Billing, Payment Settings, then the Tax info section.
3. Ads billed from abroad: the 9% goes. IRAS: you "provide your GST registration number to the vendor so that the vendor will not charge you GST on your business purchases".
4. You have nothing to reverse charge. IRAS applies the reverse charge to registered businesses "which are not entitled to full input tax claims". A business that makes only zero-rated supplies is entitled to full claims.
5. amazon.sg ads: any GST on the invoice is claimed back on your GST return.

What it costs, and when it pays

Voluntary registration in Singapore comes with conditions that have the force of law (IRAS, "Conditions for GST Voluntary Registration", January 2026):

• Before registering: complete IRAS's e-Learning course "Overview of GST" and its quiz, and apply for GIRO for GST payments and refunds. IRAS may also ask for a guarantee.
• At least 2 years. "You must remain GST-registered for at least 2 years."
• InvoiceNow. Since April 1, 2026, a business that applies for voluntary registration must send its invoice data to IRAS through InvoiceNow, whatever its structure.
• GST returns and records, like any registered business.

Say software, InvoiceNow and a bookkeeper cost you S$1,200 a year (our assumption, not an official figure):

Registering pays from about S$1,100 of ads a month. Below that, the 9% you save does not cover the cost of being registered. Weigh it over the 2 years you commit to, as IRAS itself advises.

The limits you need to know

Nothing is refunded for the past. Count on the savings from your registration date on. Amazon refunds tax only with proof that "registration was active during the billing period".

If you sell in Singapore yourself, you charge 9% GST on those sales. IRAS: "Once you are GST-registered, you will have to charge and collect GST from your customers." Books you sell at a fair, from your website or to a local shop then carry GST. For an author whose income is KDP royalties, this rarely bites. For a seller of goods to Singapore consumers, it can wipe out the gain. Prices unchanged:

That seller loses about S$323 a month by registering. Registering pays when your income carries no GST, which is the case of KDP royalties paid from abroad.

Merch on Demand: the same reasoning holds only if your Merch royalties, like KDP royalties, come from an Amazon company outside Singapore. Check your Merch agreement with your tax adviser before you count on it.

Frequently asked questions

Do I charge GST on my KDP royalties once registered?

No. Royalties paid by Amazon companies outside Singapore are zero-rated as international services under section 21(3)(j): you charge 0%.

Can I cancel after a year if it does not pay?

No. IRAS: "You must remain GST-registered for at least 2 years." Do the sums over the full 2 years before you apply.

Will Amazon refund the GST I already paid?

Only for billing periods when your GST registration was already active. Ads billed before your registration date are not covered.

I spend S$300 a month on ads. Should I register?

Not for this reason: you would save S$324 a year, far less than the cost of two years of GST returns and InvoiceNow. Run your own figures in the calculator.

Before you decide

Work out what you lose with our free calculator: enter your monthly ad spend, see the GST you pay each year and what registering would change. Then take the figure to your tax adviser.

Spending less on ads for the same sales helps too: see how much Sponsored Products ads cost and whether KDP authors can run Sponsored Brands ads. Authors elsewhere: Australia, New Zealand, Canada.

Sources

• Current GST rates, IRAS
• Factors to consider before registering voluntarily for GST, IRAS
• e-Tax Guide: Conditions for GST Voluntary Registration, IRAS, January 30, 2026
• GST InvoiceNow Requirement, IRAS
• Providing international services (section 21(3)(j)), IRAS
• Purchasing remote services from overseas service providers, IRAS
• GST and digital economy: local businesses (reverse charge), IRAS
• Amazon Advertising Agreement ("Amazon Contracting Party", "Elected Country"), Amazon Ads
• Understanding taxes and regulatory fees on your advertising invoice, Amazon Ads
• Register your Tax ID and Tax refunds, Amazon Ads help
• KDP Terms and Conditions (the Amazon parties, royalties), Amazon KDP

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