Staff Software Engineer, Payments Acquiring

Block • Seattle, WA

4d • Hybrid

About The Position

The Financial Platform Acquiring team at Block owns the acquiring side of card payments for Square, Cash App, and Afterpay. This team ensures that card payments made through Square sellers, Afterpay, or for moving money in/out of Cash App are processed correctly. Their responsibilities include taking in and tokenizing card data, routing payments, and handling authorization, capture, clearing, and settlement in the US and internationally. Block processed nearly $260 billion in payment volume in 2025 across Square and Cash App, operating direct connections to card networks in several countries. The Staff Software Engineer role focuses on complex technical work within the card payment stack, including expanding direct network and acquirer connections, delivering network mandates, and improving the cost and reliability of card acceptance. This is a hands-on role requiring deep expertise in card payments at the message level, building systems, tooling, and debugging at the protocol level. The engineer will lead projects, contribute to technical direction, and mentor other engineers. The role involves on-call responsibilities for critical financial systems.

Requirements

• 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.
• 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.

Nice To Haves

• ISO 20022 is a plus.

Responsibilities

• 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.

Benefits

• 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.

What This Job Offers

• Job Type: Full-time
• Career Level: Senior
• Education Level: No Education Listed