Sphere Is Hiring Engineers to Build the AI-Native Tax Engine
By
Samantha Cox
•
Tax compliance is one of those problems that sounds mundane until you look at the technical surface underneath. There are over 190 sovereign jurisdictions writing trade and tax rules in different languages, changing constantly, reacting to each other. Think of it as a complex adaptive system, not a lookup table. Over 190 sovereign jurisdictions writing rules in different languages, constantly shifting, constantly reacting to each other. Legacy vendors have been throwing lawyers and manual processes at it for decades.
Sphere is taking a different approach. They have built an AI-native tax engine that ingests global trade law, interprets it, resolves conflicts across jurisdictions, and produces compliance determinations with full citations and reasoning. Then human tax experts review every output before it hits production. The AI reasons. Experts decide. The engine executes. There are zero hallucinations in the production path.
The company calls their core model TRAM, which stands for Tax Review and Assessment Model. TRAM continuously collects statute law, regulations, administrative guidance, bulletins, case law, and private letter rulings from official government sources around the world. When a jurisdiction updates its rules, the system detects the change and flags every affected determination for review. This is multi-step legal analysis across jurisdictions at scale.
What Does Sphere Do?
Sphere puts indirect tax compliance on autopilot for companies that sell globally. Their platform handles the entire compliance lifecycle across sales tax, VAT, and GST.
It starts with monitoring, tracking where a company has triggered economic or physical nexus across jurisdictions. From there, Sphere handles registration with tax authorities worldwide through direct integrations, not through third-party advisory networks. The platform calculates the correct tax at the point of transaction, powered by TRAM. It files timely, compliant submissions to over 100 tax authorities. And it manages remittance, handling global tax payments from a single platform.
The key technical differentiator is that Sphere built direct local rails into over 100 tax authorities. Most competitors either cover only the United States or hand customers off to third-party consultants for international jurisdictions. Sphere handles everything end-to-end, natively. The platform sets up in less than 24 hours and integrates with major billing systems like Stripe and Chargebee, pulling transaction data to assess global tax exposure automatically.
Who Uses Sphere?
Some of the fastest-growing companies in tech run their tax compliance through Sphere. Their customer list includes Replit, Eleven Labs, Runway AI, Lovable, Windsurf, Fathom, Linktree, Photoroom, Sierra AI, and Zed.
Sphere is growing at over 34% month over month in revenue. The demand is real and compounding. Businesses are expanding internationally faster than ever, while tax authorities worldwide are tightening enforcement on cross-border compliance. Every new country a company sells into creates a new web of obligations, and Sphere is the platform that makes that expansion possible without building an internal tax team.
The Team and Funding
Sphere was founded by Nicholas Rudder. Before Sphere, Rudder built an educational marketplace called ScholarSite, where he kept running into the same cross-border compliance headaches firsthand. Instead of accepting the status quo, he pivoted the company to build the infrastructure that was missing.
The team is currently around 50 people, headquartered in San Francisco and working in-office five days a week. They closed a $21M Series A led by Andreessen Horowitz (a16z) in November 2025, bringing total funding to $25.3M. Other backers include Y Combinator, Felicis Ventures, Uncommon Capital, Pioneer Fund, and Folklore Ventures.
Why Should Engineers Pay Attention to Sphere?
This isn't a company where engineers maintain a CRUD app and push minor features. Sphere is building financial infrastructure that processes tens of millions of transactions today and is scaling toward billions. The technical challenges are genuinely hard.
Real-time tax calculation needs to happen at millisecond latency with zero downtime. The AI systems have to reason through conflicting legal frameworks across jurisdictions. The platform maintains direct integrations with government tax portals around the world, each with its own quirks, formats, and submission requirements. And the data pipeline that feeds TRAM has to continuously collect, parse, and codify unstructured legal text from hundreds of official sources.
The product roadmap extends well beyond indirect tax. Sphere is expanding into input tax, withholding tax, e-invoicing, and tariffs. Each new area multiplies the complexity and the engineering surface. The company describes its vision as building "the Deel for international billing," and the scope of that ambition means there is an unusual amount of ownership available for engineers who join now.
Everyone on the engineering team owns a domain that would be an entire team at a larger company. There is no hand-holding, no waiting for instructions, and no "good enough" shipping. Small errors have outsized impact when you are handling a company's tax obligations. The bar for precision is high, and the pace is fast.
Open Roles at Sphere
Sphere is actively hiring engineers through Fonzi across four roles. All are based in San Francisco (in-person, five days a week) with salary ranges of $200K to $250K.
Lead AI Engineer
This role owns the development of TRAM, Sphere's proprietary tax reasoning model. Day to day, that means building features to increase test-time accuracy, working on the underlying data and retrieval pipelines, and collaborating directly with internal tax experts to understand how TRAM can better reason through the tax research process. Over time, you will own TRAM's eval framework and work with frontier labs to reinforce fine-tune models on proprietary data.
The requirements are prior experience building AI-enabled products (particularly RAG systems), experience fine-tuning base models (ideally via RFT), and a willingness to go deep on tax-technical problems. If you are not interested in understanding how the model should reason through legal analysis, this role will not be the right fit.
Founding Product Engineer
This is a front-end-heavy role that owns the entire customer experience at Sphere. You will work directly with customers, the design team, and the CEO to ship features daily. The job starts with listening to customers, identifying their pain points, collaborating with design, and executing end-to-end. Within months, you will own the product roadmap and build out more rigorous feedback and prioritization processes.
Strong React and Figma experience are required. You also need to genuinely enjoy talking to people in finance roles (controllers, heads of finance, heads of tax) because you will be doing a lot of it. Attention to detail is non-negotiable when every number on the screen matters.
Senior Backend Engineer (Infrastructure)
As Sphere scales to support millions of customer transactions globally, this role focuses on the infrastructure that powers real-time tax calculation within checkout and invoice flows. You will solve the toughest scaling, performance, and latency problems, work directly with customers like Eleven Labs and Replit on their availability requirements, and build the next generation of Sphere's database, queue, and container orchestration infrastructure.
The tech stack includes Amazon Aurora PostgreSQL, ECS/EKS, Temporal, AWS SQS, Elasticache Redis, S3, and Terraform. Experience managing Kubernetes clusters at scale and shipping high-availability architectures for mission-critical systems is required.
Senior Full Stack Engineer
This is a versatile role that moves across different mission-critical areas of the platform, from filing infrastructure to the tax engine to new product areas like input tax and e-invoicing. You will ship features related to a key component, own and manage that component, and work directly with customers to improve it. Over time, you will develop expertise across multiple areas and lead other engineers in the domains you have built.
Python and Django are the core of the backend. You don't need to be a frontend specialist, but you shouldn't be afraid to jump into React when the work calls for it. Your contributions will have a direct, measurable impact on ARR growth.
What's the Culture Like?
Sphere is explicit about what they value. They hire for grit over pedigree. They ship fast (if it can be done today, they do it today). They hold engineers accountable to objective, measurable targets each month. The office is five days a week in San Francisco, and they frame that as a feature of how the work gets done, not as a policy to endure.
The team is flat. Everyone builds. If you are looking for a management track or need heavy structure to be productive, this is probably not the right environment. If you want to own hard problems at a company where your work matters and the technical surface keeps expanding, Sphere is worth a serious look.
How to Apply
Sphere is hiring through Fonzi. You can apply to be matched with Sphere and other top AI startups and tech companies through our weekly matching process. Apply once, and the Fonzi team handles curated introductions, interview coordination, and support throughout the process.
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