Accounts Payable Manager

About Radiant 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.About

the Role 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 (Quick Books, 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 Quick Books, 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, Quick Books 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…