Accounts Payable (AP) Specialist

Castelion; Torrance (CA); On-site; USD 70,000 - 90,000; Full time

Job summary

Castelion is seeking an experienced Accounts Payable Specialist to join our growing accounting team in Torrance. You will ensure accurate processing of vendor invoices, payments, and employee expense reports, while maintaining strong internal controls.

The ideal candidate brings 3+ years in AP, GAAP knowledge, and proficiency with NetSuite, Ramp, Silkline, and Excel. You will collaborate with Supply Chain and Engineering to resolve discrepancies and support monthly close. [e-mail].

Qualifications

• 3+ years of accounts payable experience, preferably in manufacturing, aerospace, or defense.
• Strong understanding of GAAP and accounting processes related to AP.
• Proficiency with ERP systems (NetSuite preferred), expense management platforms (Ramp), procurement platforms (Silkline), and Excel.

Responsibilities

• Review, code, and process vendor invoices in compliance with company policies and procedures.
• Manage the AP inbox and vendor communications, ensuring timely responses.
• Assist with the three-way matching process (PO, receipt, and invoice) and resolve discrepancies.
• Partner with Supply Chain and Engineering departments to reconcile item receipts, including quantities and prices.
• Confirm vendor payment details and process check runs, ACH payments, and wire transfers.
• Reconcile vendor statements and follow up on outstanding balances.
• Ensure compliance with internal controls and audit requirements.
• Support close activities, including AP accruals.
• Manage the employee corporate card program, including processing monthly expense reports and reimbursements.

Skills

Accounts payable

GAAP knowledge

Attention to detail

Organizational skills

Communication skills

Problem solving

Tools

NetSuite

Ramp

Silkline

Excel

Job description

Why Castelion, Why Now

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability.

Why Castelion, Why Now

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability.

Accounts Payable (AP) Specialist

We are seeking an experienced Accounts Payable (AP) Specialist to join our growing accounting team. This will be the second AP Specialist on the team and will directly support our Senior Accounting Manager. The AP Specialist will be responsible for ensuring accurate and timely processing of vendor invoices, payments, and employee expense reports. The ideal candidate is detail-oriented, organized, and thrives in a fast-paced, hands-on environment where accuracy and accountability are critical.

Responsibilities

• Review, code, and process vendor invoices in compliance with company policies and procedures.
• Manage the AP inbox and vendor communications, ensuring timely responses.
• Assist with the three-way matching process (PO, receipt, and invoice) and resolve discrepancies.
• Partner with Supply Chain and Engineering departments to reconcile item receipts, including quantities and prices, between procurement and expense management platforms.
• Confirm vendor payment details and process check runs, ACH payments, and wire transfers to ensure timely payment of invoices.
• Reconcile vendor statements and follow up on outstanding balances.
• Ensure compliance with internal controls and audit requirements.
• Support monthly, quarterly, and year-end close activities, including AP accruals.
• Manage the employee corporate card program, including processing monthly expense reports, employee reimbursements, and corporate credit card reconciliations.
• Provide ad hoc support to the Senior Accounting Manager as needed.

Basic Qualifications

• 3+ years of accounts payable experience, preferably in manufacturing, aerospace, or defense.
• Strong understanding of GAAP and accounting processes related to AP.
• Proficiency with ERP systems (NetSuite experience preferred), expense management platforms (Ramp), procurement platforms (Silkline), and Excel.
• Exceptional attention to detail, accuracy, and organizational skills.
• Strong communication and problem-solving abilities.
• Ability to thrive in a fast-paced, hands-on environment and meet tight deadlines.
• U.S. Person status required due to government program requirements.

Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details.

Other Duties

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice.

Additional Eligibility Requirements

This position may require access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply.

Affirmative Action/EEO Statement

Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law.

Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact [e-mail]. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law.

Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation.

EAR/ITAR Requirements

This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate’s ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.