Tax Manager

About Mainspring

Mainspring Energy manufactures and delivers fuel-flexible, low-emissions local power solutions that rapidly add new capacity and deliver reliable, affordable, and sustainable electric power. The company began commercial shipments of its Mainspring Linear Generators in 2020 and today has hundreds of megawatts in advanced development and field operations for leading Fortune 500 companies, data centers, and utilities. Mainspring also partners with global energy leaders including AEP, NextEra Energy Resources, Schneider Electric, and more. The core values that ground our work, guide our decisions, and connect us together: Pragmatic Optimism Excellence without Ego Proactive Collaboration

As Mainspring continues to scale, we are looking for a Tax Manager who wants to move beyond processing returns and become a true business operator. Reporting to the VP of Finance & Corporate Controller, you will build and own key tax and risk management processes that support the company’s next stage of growth. Rather than stepping into a mature tax department, you will have the opportunity to help build one. This role offers meaningful ownership, broad exposure across the business, and direct visibility with senior leadership. You will influence how Mainspring approaches tax compliance, risk management, automation, and scalability while developing the skills needed to grow into future management and leadership opportunities. This role is ideal for a technically strong tax professional who enjoys creating structure, improving processes, and taking ownership. You will partner across Finance, Legal, Operations, Sales, and FP&A while serving as Mainspring’s internal resource on tax compliance, tax reporting, and corporate insurance matters. If you are a builder who enjoys combining technical expertise with operational impact, this is an opportunity to make a lasting mark on a rapidly growing clean energy company. Key Responsibilities: Tax Compliance & Reporting Own federal and state income tax compliance activities and coordinate with external tax advisors Manage quarterly and annual ASC 740 tax provision processes Maintain tax calendars, filing schedules, and payment obligations across jurisdictions Support audits, tax notices, and inquiries from federal and state authorities Monitor tax law changes and assess business impacts Sales, Use & Property Tax Lead multi-state sales and use tax compliance, including nexus analysis and registrations Manage sales tax audits, exemptions, and documentation requirements Oversee business personal property tax filings and related compliance activities Partner with internal stakeholders to ensure accurate tax treatment of transactions and assets Risk Management & Insurance Help manage Mainspring’s corporate insurance programs, including renewals, broker relationships, and coverage reviews Support contract insurance reviews and claims management activities Partner with Legal and Operations to identify and mitigate emerging business risks Process Improvement & Scale Build and document scalable tax processes and controls Evaluate and implement tax automation tools where appropriate Bring tax activities in-house where it creates efficiency and better business visibility Help establish the foundation for a larger, more sophisticated tax and risk management function Required Qualifications 5+ years of progressive tax experience in public accounting, industry, or a combination of both Strong knowledge of ASC 740 income tax accounting and tax provision processes Experience with federal and state income tax compliance Hands-on experience with multi-state sales and use tax compliance and nexus analysis Familiarity with property tax compliance in multiple jurisdictions Ability to manage multiple deadlines and priorities independently Strong communication skills and ability to work effectively with non-tax stakeholders Preferred Qualifications Big 4 or regional public accounting experience Experience supporting manufacturing, industrial, energy, hardware, or capital equipment businesses Exposure to energy tax incentives, R&D tax credits, or other business tax credits Experience with tax technology platforms such as Avalara, Vertex, OneSource, or CorpTax Exposure to IPO readiness, public company reporting, or SOX environments Familiarity with corporate insurance programs and risk management activities