Since we opened our doors in 2009, the world of commerce has evolved immensely, and so has Square. After enabling anyone to take payments and never miss a sale, we saw sellers stymied by disparate, outmoded products and tools that wouldn’t work together. So we expanded into software and started building integrated, omnichannel solutions – to help sellers sell online, manage inventory, offer buy now, pay later functionality, book appointments, engage loyal buyers, and hire and pay staff. Across it all, we’ve embedded financial services tools at the point of sale, so merchants can access a business loan and manage their cash flow in one place. Afterpay furthers our goal to provide omnichannel tools that unlock meaningful value and growth, enabling sellers to capture the next generation shopper, increase order sizes, and compete at a larger scale. Today, we are a partner to sellers of all sizes – large, enterprise-scale businesses with complex operations, sellers just starting, as well as merchants who began selling with Square and have grown larger over time. As our sellers grow, so do our solutions. There is a massive opportunity in front of us. We’re building a significant, meaningful, and lasting business, and we are helping sellers worldwide do the same. The Role At Block, we strive to build the best financial products in the world. The Financial Platform Acquiring team owns the acquiring side of card payments for Square, Cash App, and Afterpay. When someone pays with a card at a Square seller, through Afterpay, or uses a card to move money in or out of Cash App, our systems make sure that payment happens correctly, every time. We take in and tokenize card data from chip, tap, digital wallets, and online checkout, route each payment, and get it authorized over our direct network connections and acquiring partners. Then we capture, clear, and settle it, in the US and internationally. Across Square and Cash App, Block processed nearly $260 billion in payment volume in 2025, and we run our own direct connections to card networks in several countries alongside our acquiring partners. When a customer taps their card at a register, our systems route the authorization and bring back the issuer's answer in under a second, around the clock, in partnership with card networks and bank partners. As a Staff Software Engineer on the Acquiring team, you will bring deep card payments experience to some of the most complex technical work on our roadmap. That work includes expanding our direct network and acquirer connections, delivering network mandates, and making it cheaper and more reliable to accept cards. You will lead one or two of these projects at a time. If you have worked deep in the card payment stack, at a payments company, a card network, or a large merchant, and want to own hard problems at Block's scale, this role is built for you. This is a hands-on role. You will build systems and tooling, debug at the message level, and turn your payments expertise into durable capabilities that other engineers can use. Much of the team built its payments depth here at Block. You will bring a view of how other companies solve the same problems, and learn our systems from a team that knows them deeply. In your first year, you will ship at least one of those projects to production, leave behind standards and tooling that make the next one easier, and share what you learned elsewhere so the whole team goes deeper. You will report to the engineering manager for Acquiring. This role works US West Coast hours, from our Bay Area or Seattle offices or remotely within the Pacific time zone. The team is mostly in US Eastern and Australian time zones, and Pacific hours overlap with US Eastern in the morning and with Melbourne in the late afternoon. You Will • Bring deep card acceptance expertise to the team, reading network specifications, ISO 8583 messages, mandates, and interchange rules, and turning them into sound engineering decisions. • Own the technical direction of your projects from design through production rollout, and lead the engineers working on them. • Partner with our technical leads, product and finance operations partners, and stakeholders across Square, Cash App, and Afterpay to shape solutions where card-network requirements intersect with Block's acquiring platform. • Stay deeply hands-on: write production code, build testing and certification tooling, analyze network messages, review designs and code, and debug issues down to the protocol and field level. • Make and defend the technical calls on routing, retries, and processing cost, backed by data on authorization rates and fees. • Establish shared frameworks, standards, tooling, and practices that make payments expertise durable so the team makes good payments decisions without routing every question through you. • Raise the technical capability of engineers around you through design guidance, code reviews, mentorship, documentation, and clear technical judgment. Help grow the next staff engineers on the team. • Build with AI agents across the engineering lifecycle, and help set the patterns for using them safely on systems that move money. • Share operational ownership of critical financial systems through on-call, incident response, and continuous improvements to reliability and correctness You Have • Deep card payments experience at the message level: you have built or run the integrations that talk to networks, acquirers, or processors (ISO 8583 or an acquirer's host format), not only called a payment provider's API. Acquiring or merchant-side experience is ideal, and a direct network connection is a strong plus. ISO 20022 is a plus. • Experience with the hard cases in real card transactions, such as partial and incremental authorizations, reversals, tips, currency conversion, and interchange qualification. • Strong hands-on software engineering experience building and operating highly reliable financial or payments systems at scale, with solid habits in design review, automated testing, and safe, observable rollouts. • A track record of leading technically complex projects from design through delivery and setting technical direction for the engineers working on them. • Experience creating durable technical leverage — frameworks, standards, tooling, architecture, or practices that other engineers and teams adopt. • Broad understanding of how a card payment moves end to end, with depth in areas such as card data security and tokenization, routing, authorization, capture, clearing and settlement, reconciliation, interchange and processing costs, or chargebacks. • Solid understanding of card network rules (Visa, Mastercard, American Express, Discover, and US debit networks), and of how acquirers, processors, payment facilitators, and sponsor banks fit between sellers and the networks. • Daily experience building with AI coding agents, and good judgment about when their output is right. • Willingness to participate in an on-call rotation for critical financial systems. We’re working to build a more inclusive economy where our customers have equal access to opportunity, and we strive to live by these same values in building our workplace. Block is an equal opportunity employer evaluating all employees and job applicants without regard to identity or any legally protected class. We will consider qualified applicants with arrest or conviction records for employment in accordance with state and local laws and “fair chance” ordinances. We believe in being fair, and are committed to an inclusive interview experience, including providing reasonable accommodations to disabled applicants throughout the recruitment process. We encourage applicants to share any needed accommodations with their recruiter, who will treat these requests as confidentially as possible. Want to learn more about what we’re doing to build a workplace that is fair and square? Check out our I+D page. Whil…