Software Engineer, Tax

Aiwyn

1d•Remote

About The Position

Aiwyn is the first complete platform for modern Accounting Firms. Backed by top-tier investors like Bessemer, KKR, and Revolution, we're one of the fastest-growing scale-up SaaS companies in the world. We build category-defining technology, and we're doing it with world-class people, processes, and products. We work with the majority of the Top 500 firms in the country. We're replacing 40-year-old tax engines and brittle integrations with software accounting firms can actually trust, and we have rare product-market fit in an industry that's about to change permanently. We're hiring a senior software engineer to join the team that owns our tax engine: the calculation core that's already filed over a million returns and is now the wedge that lets us own the entire return end to end. The tax engine is one of the most strategic pieces of IP at Aiwyn, and the foundation we're opening up to AI labs and modern firms who want a tax engine they can build on top of. We built TaxCalcBench, which has become how the AI labs measure their frontier models on tax calculation, and Anthropic came to us to ship Aiwyn Tax as a Claude Connector. The next milestone is full 1040 coverage for every American filer, then onward into other forms — at AI-pace, with accuracy held at 100%. You'll be a senior engineer on the team behind this work, partnering closely with a deeply tenured group of CPAs and tax experts who set the bar for what "correct" means.

Requirements

5+ years of professional software engineering experience, with a track record of taking full ownership of projects from spec to ship to scale.
Hands-on technical depth in domains where correctness matters. You've shipped real systems where edge cases, accuracy, and domain depth were non-negotiable.
Demonstrated ability to bridge engineering and a non-engineering domain. Engineers and tax experts (or doctors, or lawyers, or any deep domain expert) think wildly differently. You've worked closely with non-engineering experts before, taken their judgment seriously, and built shared language and shared artifacts that let both sides do their best work. We've watched smart people struggle here, and this is the part of the job we look at hardest.
AI-native fluency. AI tooling is woven into how you work and ship, and you have a clear point of view on where it helps and where it creates noise.
Comfortable across the stack. Backend, frontend, or infrastructure — you can reason about whatever the problem actually requires.

Nice To Haves

Experience building or contributing to a rules engine, calculation engine, or comparable system. Tax, payroll, billing, pricing, underwriting, claims adjudication, compliance, benefits. Anywhere correctness is non-negotiable and the system has to compose hundreds or thousands of rules into an answer you can defend.
Tax industry experience. Direct work on a tax engine or in tax technology is a strong plus, but not required.

Responsibilities

Build the system that builds the engine. Own the agent tooling, test infrastructure, and confidence metrics that let the engine grow at speed without sacrificing accuracy. Make the iteration loop faster every cycle.
Work in the trenches with the tax experts. They've been doing this for decades. They're your closest collaborators and your toughest users. Spend real time with them, understand what it actually takes to file across federal and state jurisdictions, and translate that depth into the systems you build.
Build and extend the APIs that AI labs and modern firms build on top of. Partners are the wedge. Make integration seamless and the surface area something engineers actually want to use.
Take projects from spec to ship to scale. Own the work end to end, including the parts outside your comfort zone.