Accounts Payable Manager

Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028.

Radiant is seeking an AP Manager to own our end-to-end accounts payable operations. We process 800-1,300 invoices monthly across fragmented systems (QuickBooks, ION, and Ramp) with no automatic integration or three-way match. This role will manage the full invoice-to-payment cycle, build scalable AP infrastructure, and establish the controls and processes needed to support our growth from prototype development through production ramp.

This is a hands-on role with significant ownership. You'll process high volumes while simultaneously building the systems, controls, and documentation that will scale with the company. You'll partner closely with Supply Chain on procurement workflows and with Finance leadership on cash management strategy and ERP implementation planning.

Responsibilities & Duties:

Invoice Processing & Management

• Process 800-1,300+ invoices monthly across QuickBooks, ION, and Ramp

• Review, code, and approve invoices ensuring proper GL account assignment, project codes, and class accounting

• Perform manual three-way matching across disconnected systems until ERP implementation

• Handle employee and candidate reimbursements, corporate card reconciliations, and ad-hoc payment requests

• Manage vendor setup, W-9 collection, and vendor master data maintenance

Payment Processing & Vendor Management

• Execute payment runs to capture early payment discounts and avoid late penalties

• Serve as primary point of contact for 150+ active vendors; resolve inquiries, disputes, and statement reconciliations

• Coordinate with Procurement on vendor onboarding, contracts, and payment terms

• Monitor aging reports and resolve payment holds or exceptions

Process & Controls

• Build scalable AP infrastructure with automations where possible

• Design and document AP policies, procedures, and workflows for a scaling organization

• Implement approval matrices, segregation of duties, and fraud prevention controls

• Build audit-ready documentation and support external audits

System Optimization & ERP Readiness

• Maximize functionality of existing tools: Ramp Pro automation, ION workflows, QuickBooks coding rules

• Document current-state processes and pain points to inform 2026 ERP requirements

• Lead AP workstream for ERP selection, implementation, and data migration

Compliance & Cross-Functional Partnership

• Maintain 1099 vendor tracking and support sales/use tax compliance and annual filings

• Partner with Supply Chain and Receiving on purchase order workflows and vendor management

• Train employees on policies, Ramp usage, and invoice submission requirements

Required Qualifications & Skills:

• 5+ years of accounts payable experience, with at least 2 years in a senior or lead AP role

• Experience processing high-volume AP (500+ invoices/month) in a fast-paced environment

• Proficiency with AP automation tools and ERP systems

• Strong understanding of three-way match processes, GL coding, and month-end close procedures

• Experience with 1099 reporting, sales/use tax compliance, and audit support

• Track record of building or improving AP processes and controls

• Excellent attention to detail and ability to manage competing priorities

• Strong communication skills for vendor management and cross-functional collaboration

Desired Qualifications & Skills:

• Hardware, manufacturing, or aerospace/defense industry background

• Experience with government contract accounting (FAR/DFARS)

• Familiarity with Ramp, QuickBooks, and/or ION

• Experience supporting ERP implementations or system migrations

• SQL or reporting tool proficiency for building AP analytics

• Experience in high-growth companies navigating significant scale

What We're Looking For:

Ownership mentality: Takes full accountability for AP operations and proactively identifies improvements

Builder mindset: Creates scalable processes rather than just executing existing ones

Detail-oriented: Catches errors, maintains accuracy under volume pressure, and keeps clean records

Systems thinker: Understands how AP connects to procurement, receiving, and financial reporting

Adaptable: Thrives in an environment where systems are imperfect and processes are evolving

Team player: Works effectively with Supply Chain, Engineering, and Finance partners

Additional Requirements:

• Must be willing to work extended hours and weekends as necessary to accomplish our mission.

• Must work 100% onsite at El Segundo HQ.

• Stock: Substantial incentive stock plan for all full-time employees.

• Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.

• One Medical: Sponsored memberships for employees and their dependents.

• Vision: 100% top tier plan coverage + 50% for dependents.

• Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.

• Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.

• 8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.

• Nuclear Engineering Certificate Program: 100% covered educational program with Penn State University, for eligible employees, to rapidly upscale into nuclear.

• Daily catered lunch. Free snacks and drinks.

• Flexible PTO policy. Remote workday allocation.

• Company and team-bonding events, happy hours and in-person camaraderie.

• Beautiful El Segundo headquarters close to the Pacific Ocean.

Total Compensation and Benefits
Radiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s full-time new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant.
The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: [email protected].
We are an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, pregnancy, age, national origin, disability status, genetic information, protected veteran status, or any other characteristic protected by law.

This position involves access to technology that is subject to U.S. export controls. Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls.