Build It Your Way: How Zeller's Open SDK Is Changing What Developers Can Do With Payments

Build It Your Way: How Zeller's Open SDK Is Changing What Developers Can Do With Payments

Building a custom payment integration has never been easier thanks to Zeller Developer Suite. Read on to learn how one operator built a custom POS system from the ground up, then integrated it seamlessly with Zeller Terminal . When Sebastian Alarcon Pinto, an ex-computer scientist and founder of Urku , a Melbourne-based chocolate company, went looking for a point-of-sale solution, he didn't find what he needed on any shelf. So he built it himself. He coded a custom POS system complete with a loyalty program and a kitchen display system. Using Zeller Developer Suite he was then able to integrate Zeller Terminal directly into his custom-built POS, enabling it to quickly push transactions directly to the payment terminal and offer his customers QR code receipts. A seamless integration that allowed him to complete the build in record time. Removing the barrier to payment integration Until now, developers building payment integrations have either been restricted by access or deterred by complex global platforms with limited local support. Providers that orient their architecture toward their own hardware ecosystem limits what customisation is possible. And larger global providers often come with much deeper complexity both in terms of pricing and integration, which is especially frustrating for developers who only need a subset of its capabilities. Zeller Developer Suite solves this. It gives teams full SDK access from the outset, across React, React Native and Windows .NET, giving them the ability to integrate into their existing Android, iOS and Windows based applications. There are no restricted tiers to unlock, and no ceiling on what a developer can inspect or build. Documentation that developers actually use Access is only half the equation. The other half is documentation clear enough to use. This is where many payment SDKs fall short. Developers building on Zeller's SDK consistently point to the documentation as a differentiator. The logic of the transaction flow is explained and the first integration milestone is achievable quickly, without requiring a support escalation or a call with an account manager. Speed to integration For Sebastian, building a fully custom POS with loyalty programme, kitchen display system, automatic weekend service charging, and customer database took just six weeks. In the first week alone, he shipped 32 deployments. The SDK did what the documentation said it would do, consistently, from the first connection onwards. “It's just been easy — I don't have to worry about the connections, and I've never had a failed transaction,” says Sebastian. What openness enables The practical value of Zeller Developer Suite isn't just speed — it's the range of things a developer can build with it. In Sebastian’s case, that meant a two-stage transaction status system — distinguishing between payment confirmed and settlement verified — that he later evolved into a kitchen display system showing real-time order status to baristas. It also meant automatic weekend surcharging that replaced a manual process of re-entering all product prices every Friday. But perhaps what resonated most for Sebastian, was finding a platform that approached payments the same way he approaches his service: from the customer experience backwards. "When I saw that Zeller offered QR code receipts with a download option right on your phone, that told me that they work the same way I work: from the customer experience towards the functionality, not from a revenue idea backwards. That's what I really liked." Built for how you do business  Beyond the technical architecture, Zeller Developer Suite offers something that global platforms by definition cannot: infrastructure designed around Australian and UK business conditions from the ground up. Weekend service charge rules, local award rates and banking norms, and the specific compliance requirements that affect local merchants are built into Zeller's platform rather than retrofitted. For a developer building a POS or payment integration, it means the platform's defaults are closer to what their local customers actually need. What it means to build on Zeller For developers evaluating payment SDK options in Australia or the UK, Zeller Developer Suite offers full access, clear documentation, fast integration, and a platform designed for the market where their clients actually operate. Zeller's Developer Suite is available now for Terminal and Online integrations, with Tap to Pay and eCommerce support coming soon. The SDK supports React, React Native, Android, iOS, and Windows .NET.

by Team Zeller
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Latest Reports

Special Report
Zeller Invoicing Report 2025

Zeller Invoicing Report 2025

Paper and PDF invoices persist – but why? Australians have long embraced the speed, accountability, security, and transparency that electronic payments offer, with card payments making up 76 per cent of all transactions . In striking contrast, a recent report estimated that around 90% of SMEs are still sending paper-based or PDF invoices. With digital payments so deeply entrenched, why are Aussie SMEs still sending invoices that force their customers into the arduous process of opening a banking app and copy‑pasting BSBs and account numbers? It’s a fair question – especially when online invoicing solutions are far more time-efficient and result in much faster payment. How much faster, you ask? The numbers below tell a clear story. 100,000+ invoices. Four key insights. Zeller recently analysed more than 100,000 invoices sent and paid via Zeller Invoices. The data clearly demonstrates that online invoicing not only accelerates payments but also reveals important insights around industries, payment methods, delivery channels, and payment terms. This report dives into these insights, providing a guidebook for how you can  immediately improve your business cash flow. Insight 1 Invoice payment times vary across industries. When it comes to invoice payment speed, not all industries are created equal. Zeller’s data shows that on average, invoices are paid in 7.14 days, regardless of sector. Industries such as Retail, Leisure & Entertainment, Transport, and Hospitality tend to be the slowest – on average taking longer than a week for invoices to be paid. In contrast, sectors like Travel, Health & Fitness, Professional Services, and Beauty benefit from faster invoice payments, below the 7-day Australian average. Why the difference? Payment delays can depend on industry norms and client expectations. For example, retail suppliers often wait on store owners to reconcile accounts, whereas a beauty therapist or consultant may be paid immediately after the appointment. Knowing where your industry stands helps set your expectations and plan your cash flow. If you operate in a typically slow-paying sector, it’s wise to be proactive about speeding up payments (as we’ll explore in the following sections). And if you’re in a faster-paying field, there may still be room to tighten the turnaround and get paid even sooner. Practical tips Insight 2 Invoices payable by card are paid 7 times faster. One of the report’s most striking findings is the impact on payment timing by the payment methods available to  settle an invoice. Invoices that offer customers an online credit card payment option get paid dramatically faster – on average 7 times faster than invoices that only offer payment via manual bank transfer. In fact, when customers can click a secure link and pay by card, invoices are settled in just about 2.4 days on average, versus 14.5 days when only a bank transfer is offered.   This trend holds across every sector, though the degree varies. For example, in the Beauty industry, card payments got invoices paid a whopping 15 times faster, versus about 3 times faster in Retail (which is still a huge improvement). Travel businesses saw 9x faster payments with card, Food & Drink about 8.4x, and even traditionally slower sectors like Transport saw over 4x improvement. The bottom line is that, no matter your field, offering customers the choice to pay invoices by credit or debit card greatly accelerates your cash flow. Why does card payment make such a difference? It comes down to convenience and immediacy. Paying an invoice by card is frictionless for the customer – it’s just a few clicks with no need to open a banking app or remember a BSB and account number. Customers can even pay on credit (which means they don’t need cash on hand at that moment) and can potentially earn reward points for doing so. The process is faster and all in one place, especially with digital wallets like Apple Pay or Google Pay allowing for one-tap checkouts. In contrast, bank transfers introduce more steps and greater friction (opening a separate app, typing out amounts and references, ensuring funds are available), which means invoices tend to sit unpaid longer. The data illustrates this clearly. When an invoice includes a card payment link, 70% of those invoices are paid within 24 hours of being sent. With bank-transfer-only invoices, however, a mere 28% are paid on the same day – and nearly 40% of these invoices remain unpaid for over a week. That gap can be the difference between having money in your account tomorrow versus chasing customers next month. Enabling instant online payments essentially turns invoices into a quick “checkout” experience for your client, dramatically improving the odds of prompt payment. Practical tips Insight 3 Invoices sent via SMS are paid 43% faster than those issued via email. How you deliver an invoice can be almost as important as the options you provide to customers for them to make invoice payment. The data reveals that sending invoices by SMS leads to significantly faster payments than sending them by email. In fact, an invoice sent as an SMS link is paid 43% faster on average than an invoice sent via email. In other words, getting that bill directly into your customer’s phone via text message can shave substantial time off the payment turnaround. This makes sense when you consider customer behaviour. A text message is typically read within seconds, and it pops up right in front of the client – it’s hard to ignore. By contrast, an emailed invoice might sit unseen in an inbox or be deferred until “later” when the customer is at their desk. Worse, emails can get lost in spam or filtered out, meaning your client might not even see the invoice at all. With SMS, you’re putting the payment link literally in your client’s hand, on the device they check most often. It’s the most visible way to get their attention on a bill. Another important factor is mobile optimisation. If you send a text with a payment link, you can almost bet the customer will click it on their smartphone – so that invoice needs to be easy to read and pay on a small screen. A clunky or non-mobile-friendly payment page can create friction and delay payment. On the other hand, a smooth mobile checkout (think big buttons, simple form, autofilled details) encourages customers to settle the invoice immediately, perhaps even on the spot while they’re thinking about it. Zeller Invoices automatically recognises which device is being used to, meaning it works flawlessly on both mobile desktop. Timing is another factor here. The sooner the customer receives the invoice, the sooner you’re likely to get paid. Our data suggests a strong benefit to issuing the invoice as soon as a job is done or a sale is completed, rather than waiting hours or days. For instance, if you finish a service call or deliver goods, sending the invoice before you leave the client’s location can prompt immediate payment (often customers will pay while you’re still there). Prompt invoicing keeps the transaction fresh in the client’s mind and signals professionalism. Practical tips Insight 4 Longer terms don’t necessarily mean slower payment. It’s common for businesses to offer extended payment terms – such as 30 or 60 days – to valued clients or to entice new business. Intuitively, you might think giving a client two months to pay would result in getting paid closer to that 60-day deadline. Surprisingly, Zeller’s data shows that extending payment terms doesn’t significantly delay when customers actually pay. In other words, a client given 60 days isn’t guaranteed to take 60 days to pay – they often pay much sooner. In fact, invoices with 30-day terms were paid on average in about 15 days, whereas invoices with 60-day terms were paid in under 20 days on average.  What does this mean for you? First, offering extremely long terms (beyond 30 days) may not be necessary in many cases, since clients aren’t likely to fully utilise that extra time. If a customer is going to pay you in about two to three weeks regardless, then giving them two months to pay is more of a courtesy than a requirement, and it could unnecessarily strain your cash flow. Remember that when you extend long payment terms, you’re effectively extending credit to your customer and financing their operations in the meantime. That can leave you footing the bill for expenses (like goods sold or staff wages) while you wait for the money to come in. Secondly, the fact that longer terms don’t necessarily mean later payments presents an opportunity – you might be able to negotiate shorter terms without upsetting customers, especially if you’ve noticed they typically pay early anyway. For instance, if a client consistently pays your 30-day invoice in two weeks, that’s a signal that you could propose a 14-day term moving forward, formalising what’s already happening in practice. This protects your cash flow with minimal impact on the customer, who has shown they don’t really need the extra time anyway. Of course, some clients will still push right up to the deadline (and a few will be late payers regardless of terms). The key is to know your customers. Use your invoicing data or reports to identify who pays when. You might find some always pay early (or on time), while others chronically drag their feet. You can then manage each accordingly. Perhaps rewarding prompt payers with a small discount for early payment, or enforcing late fees for stragglers, as appropriate. Practical tips