Usage-based billing in Singapore: 2026 guide

Key takeaways:

• Usage-based billing charges customers based on how much they use a product or service. The tricky part is tracking that usage accurately, not calculating the bill.

• Usage invoices still need to meet Singapore’s GST requirements. InvoiceNow e-invoicing is also being rolled out in phases for GST-registered businesses.

• Airwallex Usage-Based Billing helps businesses track usage, issue invoices, and collect payments in multiple currencies from one platform.

Usage-based billing in Singapore is no longer just for cloud providers and telcos.

Software, API, and AI businesses are increasingly charging customers by the API call, token, or task, so monthly bills can change depending on how much each customer uses.

This guide covers how usage-based billing works, what Singapore businesses need to consider, and how to get started. You’ll learn about GST requirements for usage invoices, collecting payments in multiple currencies, billing for AI startups, and choosing the right billing software.

What is usage-based billing?

Usage-based billing (UBB) means charging customers for what they actually use.

Depending on your product, that might mean API calls, AI tokens, gigabytes of storage, or messages sent. The amount a customer pays changes each billing period based on their usage.

With a traditional subscription, customers pay a fixed fee regardless of how much they use. Usage-based billing can work alongside a subscription too, with a base fee plus extra charges for usage.

You may also come across a few related terms. They describe similar concepts, but each has a slightly different focus:

This guide focuses on the billing process: turning usage data into an invoice. For a closer look at per-unit, tiered, volume, and hybrid pricing, read our guide to usage-based pricing models in Singapore.

How usage-based billing works

Usage-based billing takes a customer’s activity and turns it into an invoice through four steps. Errors at any stage can affect the final amount, so it’s important to get each one right.

1. Capture usage events

Whenever a customer takes a billable action, such as making an API call or completing a task, your product records it as an event. Each event should include the customer, action, timestamp, and quantity.

Missing or duplicated events, or events linked to the wrong customer, can lead to incorrect bills.

2. Aggregate usage with meters

A meter adds up recorded events over a billing period, such as the total AI tokens a customer uses in a month.

One thing to watch for is late-arriving data: decide whether usage recorded after the period closes belongs on the current invoice or the next one, and apply that rule consistently. For more detail, read our guide to metered billing in Singapore.

3. Calculate charges based on your prices

Once usage is totalled, the billing system applies your pricing rules to calculate the amount due. Things can get complicated when customers change plans mid-cycle, or when discounts and credits apply to only some of their usage.

4. Generate the invoice and collect payment

The system turns those charges into an invoice, showing customers how the total was calculated, and then collects payment. Itemised charges make it easier for customers to check their usage and understand what they’re paying for.

Singapore businesses also need to follow local invoice requirements, which we cover below.

Checklist: Is your business ready to bill by usage?

Before switching to usage-based billing, make sure your systems and processes can handle it. Use this checklist to spot gaps you should address before you start.

• Event capture. Can you record every billable event without missing or duplicating it? Either can lead to incorrect invoices.

• Customer attribution. Can you link each event to the right customer, plan, and price? This can get more complicated when accounts are shared or customers have multiple entities.

• Invoice clarity. Can customers see the units used, rates charged, and totals for each line item? Clear breakdowns make invoices easier to check and help prevent disputes.

• Disputes and credits. Do you have a clear process for correcting billing errors and issuing credit notes? Decide who approves adjustments and how quickly they should be handled.

• Finance visibility. Can your finance team see accrued usage before invoices go out? This helps with forecasting and month-end close.

• Tax and currency. Can your system generate GST-compliant invoices and handle payments in different currencies? We cover these requirements in the next two sections.

• Bill shock prevention. Can customers check their usage and estimated charges during the billing cycle? Giving them visibility helps avoid unexpected bills and builds trust.

Usage-based billing and GST in Singapore

Usage-based invoices follow the same GST rules as other invoices. The main difference is that charges change each billing cycle, so your system needs to calculate GST correctly every time.

GST on usage charges

Singapore’s standard GST rate is 9%¹, and you generally charge GST on local supplies.

For overseas customers, you may be able to apply 0% GST if the service qualifies as an international service under section 21(3) of the GST Act. However, the service must not be directly connected with land or goods in Singapore. 

Check the rules that apply to your service before zero-rating a sale².

Tax invoices for usage

You generally need to issue a tax invoice to a GST-registered customer within 30 days of the time of supply. It must include details such as your GST registration number, the GST rate, the amounts before and after GST, and a description of the services¹.

Because usage accumulates throughout a billing period, confirm with your tax adviser which date counts as the time of supply under your contracts. Breaking charges down by meter, with the units used and rate applied, also helps customers check their invoices.

For the full list of fields and formats, read our guide to GST invoice requirements in Singapore.

Foreign currency invoices

If you issue an invoice in a foreign currency, you must show three amounts in SGD: the total excluding GST, the GST amount, and the total including GST. Use exchange rates approved by IRAS for GST purposes¹.

Credit notes and adjustments

Issue a credit note when you correct a usage charge or resolve a billing dispute. Under InvoiceNow, you must also submit credit note data to IRAS, even if the adjustment does not change the GST amount³.

GST InvoiceNow

GST-registered businesses must submit invoice data to IRAS through an InvoiceNow-Ready Solution, with the requirements being introduced in phases³. For existing businesses, the start date depends on their total annual supplies in 2025.

Usage-based billing can generate long invoices. IRAS recommends keeping each invoice to no more than 999 line items, and each submission file must be under 10MB. For overseas customers, you must also record their business registration number³.

For a full explanation of how InvoiceNow works and how to get set up, read our guide to InvoiceNow in Singapore.

Billing customers in multiple currencies and getting paid

Usage-based billing can delay cash flow. You deliver the service first, then invoice the customer, so payment may arrive weeks after the usage occurs.

If you bill in a foreign currency, exchange rate movements during that period can also affect how much you receive in SGD.

How exchange rates affect your revenue

Suppose you invoice a US customer for US$10,000 at the end of a 30-day billing cycle, with another 30 days to pay. By the time the money arrives, some of the usage could be almost 60 days old. Here’s how it might look:

Illustrative example only. These exchange rates are not forecasts.

The rate could also move in your favour, but either outcome makes cash flow harder to predict. This matters most when your costs, such as cloud hosting or compute, are in a different currency from your revenue.

Choosing how to collect variable amounts

Because the invoice total changes each cycle, your collection method affects how you manage payment risk.

Prepaid credits reduce payment delays on the amount collected upfront, because customers pay before using the service.

Holding funds in the currency you are paid

Billing customers in their own currency means they may not need to convert funds before paying. Holding those funds in the same currency can also help you avoid converting them as soon as payment arrives.

Airwallex Cash Accounts provide local bank details to receive funds in 20+ currencies. The platform also supports like-for-like settlement in 14 currencies, allowing you to hold funds and choose when to convert them, rather than converting each payment as it arrives.

Usage-based billing for AI startups in Singapore

Many AI startups in Singapore sell to customers across Asia and beyond from the outset. They may charge by tokens, API calls, or completed tasks, with usage varying from one billing cycle to the next.

Because every request also has a compute cost, billing needs to keep pace with usage and help prevent unexpected charges. Here’s what you need to know:

Credit wallets

Many AI products let customers buy credits upfront and deduct usage from their balance.

Before launching this model, decide what happens when the balance reaches zero. You could pause the service, let customers continue on pay-as-you-go billing, or automatically top up their credits.

You should also set clear rules for whether credits expire and explain them before customers buy. Ask your accountant how to account for unused or expired credits.

Spend controls

Different controls address different billing risks. Most AI products will need a combination of them:

Managing costs and revenue across currencies

Compute costs are often billed in USD. If you charge customers in SGD or another currency, exchange rate movements can affect your margins.

Where customers are willing to pay in USD, billing in that currency can reduce the need to convert revenue before paying your compute costs. Otherwise, review your pricing regularly to check that your rates still cover your costs.

Handling late and duplicate usage events

AI products can generate large volumes of usage events, and some events may arrive late or be recorded more than once. Set clear rules for handling both cases before you start billing.

For example, you could carry late events into the next invoice, provided your billing terms explain how these adjustments work. Your system should also identify duplicate events so the same usage is never charged twice.

How to prevent bill shock and billing disputes

Bill shock happens when customers receive invoices that are much higher than they expected. Many disputes can be avoided by giving customers visibility into their usage and charges before the bill arrives:

• Show usage throughout the billing cycle. Give customers a dashboard or report where they can track usage as it accumulates, rather than seeing the total for the first time on their invoice.

• Send usage alerts. Notify customers when they reach set thresholds, and include the estimated cost so they know how much they may owe.

• Break down invoice charges. Show the units used, rate, and subtotal for each meter. This helps customers check charges against their own usage records.

• Communicate changes in advance. Tell customers about changes to pricing or how usage is measured before the next billing cycle begins.

• Make disputes easy to resolve. Provide a clear process for raising billing questions, reviewing usage, and issuing credit notes. Set expectations for response times.

Keep a record of why disputes occur. If the same issues keep coming up, review your usage tracking and invoice layout to find the cause.

How to choose usage-based billing software in Singapore

The right usage-based billing software depends on how you measure usage, who you bill, and which currencies you accept. If you’re comparing tools for a Singapore business, start with the requirements below:

Before committing, run a month of historical usage through each tool you’re considering. Compare the results against your own records to check for differences in usage totals and charges.

Types of usage-based billing tools

Different tools handle different parts of the billing process.

Payment processors may include usage metering in their billing products, while dedicated billing engines focus on usage tracking and pricing rules and may require a separate payment solution. Subscription billing platforms let you add usage charges to recurring plans.

Consider how much of your revenue comes from usage-based charges, how complex your pricing is, and how much engineering time you can dedicate to maintaining the system.

For a side-by-side comparison of providers, see our guide to the best subscription billing software in Singapore.

Why Singapore companies choose Airwallex for usage-based billing

With Airwallex Usage-Based Billing, you can launch usage pricing without building your own metering and invoicing system. Here is how a typical setup works.

1. Create a meter. Choose the usage event to track and how to aggregate it: sum, count, unique count, maximum, or latest value. You can’t change a meter’s aggregation logic after you create it, so plan this step carefully.

2. Create a product and price. Link a usage-based price to your meter. We support per-unit, volume, and graduated tiered pricing.

3. Create a billing customer. Add the customer you want to charge.

4. Create a subscription. Attach the usage-based price to that customer’s subscription.

5. Send usage events. Send events through our API as usage happens. You can also submit events for multiple customers in a single batch request.

At the end of each cycle, we aggregate the usage and generate the invoice automatically.

Events that arrive within one hour after the period ends are still included. If you send an event by mistake, you can void it for up to 35 days. Voiding does not change an invoice that is already final, so issue a credit note in that case.

Frequently asked questions (FAQs)

Is usage-based billing the same as consumption billing or metered billing?

Usage-based billing and consumption billing mean the same thing: charging customers for what they use. Metered billing is slightly different, because it describes the tracking that measures usage and feeds the invoice. In practice, any business that bills by usage in Singapore relies on metering to do it.

Is usage-based billing suitable for small businesses in Singapore?

Yes, if your customers’ usage varies from month to month and you can measure it accurately. Small teams should check the readiness points earlier in this guide first, especially event capture and itemised invoices. Airwallex Usage-Based Billing lets you set up meters and automatic invoicing without building your own billing system.

Do I charge GST on usage-based invoices in Singapore?

If you are GST-registered, you charge 9% GST on usage supplied to customers in Singapore¹. Services supplied to overseas customers may qualify for 0% GST as international services, but only if they meet the conditions². Check the IRAS rules for your own service before you zero-rate it.

Do usage-based invoices have to go through InvoiceNow?

Yes, if you are GST-registered, though your start date depends on your phase. IRAS is phasing in the GST InvoiceNow requirement from November 2025 for some new registrants, and from April 2028 to April 2031 for other GST-registered businesses³. Check your phase, and make sure your billing tool can send invoice data to an InvoiceNow-Ready Solution.

How do I invoice for usage in USD from Singapore?

You can issue the invoice in USD, but if you are GST-registered, the tax invoice must also show three amounts in SGD: the total excluding GST, the GST, and the total including GST. Use the exchange rates that IRAS approves for GST purposes¹. A billing tool that handles this conversion saves manual work every cycle.

How do I avoid bill shock with usage-based billing?

Show customers their usage while it builds up, not only on invoice day. Send alerts at thresholds you set, itemise every invoice, and tell customers about rate changes before the cycle starts. Prepaid credits or spend caps also give customers a fixed limit. Airwallex also lets you query a customer’s aggregated usage before an invoice goes out.

Sources:

1. https://www.iras.gov.sg/taxes/goods-services-tax-(gst)/basics-of-gst/invoicing-price-display-and-record-keeping/invoicing-customers

2. https://www.iras.gov.sg/taxes/goods-services-tax-(gst)/specific-business-sectors/e-commerce

3. https://www.iras.gov.sg/media/docs/default-source/uploadedfiles/gst/frequently-asked-questions-for-gst-invoicenow-requirement.pdf