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Invoice Checklist
Twenty things to check before you send. Most delayed payments are not disputes, they are invoices missing something the client's accounts team needs, which sends the whole thing back to the bottom of a pile. Tick as you go and the summary at the bottom tells you what is still outstanding.
How to Use This Checklist
This checklist covers every field a legally compliant invoice needs in Singapore and Malaysia. Work through it before sending any invoice to a new client or for a new project type.
Singapore invoices must include your UEN (Unique Entity Number) if you are GST-registered, the 9% GST line item, and your IRAS GST registration number. Non-GST-registered freelancers should omit the GST line entirely rather than charging 0% GST, which can mislead clients.
Malaysia invoices must include your SST registration number if applicable. LHDN has been phasing in the MyInvois e-invoicing mandate by turnover band since August 2024, reaching businesses above RM1 million in January 2026. Check the LHDN site for the phase that applies to you.
General rule: Keep invoice records for at least 5 years in Singapore, which is what IRAS requires. Malaysia is longer. Section 82A of the Income Tax Act 1967 requires 7 years, so work to the 7 year figure if you invoice into both countries.
Sources: On what a tax invoice must contain, the GST registration threshold, and the requirement to keep business records for at least five years, see the Inland Revenue Authority of Singapore guidance on invoicing customers. On business registration and Unique Entity Numbers, see the Accounting and Corporate Regulatory Authority. Rates and thresholds change, so confirm current figures at the source before relying on them.
How the Checklist Works and When to Use It
The checklist walks the fields an invoice needs before it goes out, grouped in the order a client reads them: who is billing, who is being billed, what the work was, what is owed, and how to pay. Ticking through it takes under a minute and catches the omissions that actually delay payment, most often a missing invoice number, an unclear due date, or bank details buried at the bottom.
Use it the first few times you invoice a new client, and again whenever you change your terms or start charging GST. Freelancers, contractors and small business owners all hit the same failure mode: an invoice that looks complete but gives the client a reason to park it in a queue.
The mandatory fields differ depending on whether you are GST registered. IRAS guidance on invoicing customers specifies what a tax invoice must show, including the GST registration number and the tax amount, and an invoice missing those cannot be used by your client to claim input tax.
A practical way to use it is to run the checklist once and then save the resulting invoice as your template, so the fields carry forward and you are only changing the client, the dates and the line items each time. That removes most of the risk of omission without needing to re-check every field. If you later register for GST, or start invoicing clients outside Singapore, run the checklist again from scratch, because both changes add fields that a template built earlier will not contain.