Accounts Payable Manager

Radiant•El Segundo, CA

11d•Onsite

About The Position

Radiant is an El Segundo, CA-based startup building the world’s first mass-produced, portable nuclear microreactors. The company’s first reactor, Kaleidos, is a 1-megawatt failsafe microreactor that can be transported anywhere power is needed and run for up to five years without the need to refuel. Portable nuclear power with rapid deploy capability can replace similar-sized diesel generators, and provide critical asset support for hospitals, data centers, remote sites, and military bases. Radiant’s unique, practical approach to nuclear development utilizes modern software engineering to rapidly achieve safe, factory-built microreactors that leverage existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor next year at the Idaho National Laboratory, with initial customer deliveries 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.

Requirements

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

Nice To Haves

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

Responsibilities

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
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
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
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
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

Benefits

Stock: Substantial incentive stock plan for all full-time employees.
Medical: 100% premium coverage for base Silver level plan for employee + 50% premium coverage for dependents. Platinum plans available.
One Medical: Sponsored memberships for eligible employees and their dependents.
Vision: 100% premium coverage for top tier plan + 50% for dependents.
Dental: 100% premium coverage for top tier plan (including orthodontia) + 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.
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.