About Mariana Minerals

Mariana Minerals is a software-first, vertically integrated minerals company on a mission to supply the critical minerals powering modern energy, AI, and defense technologies. We’re reimagining the minerals supply chain by combining deep industry expertise with advanced software, automation, and data-driven decision-making.

The Role

We are seeking an experienced Accounts Payable Manager to lead Mariana Minerals’ accounts payable operations and help build a scalable, technology-enabled procure-to-pay function. This position is responsible for ensuring the timely and accurate processing of supplier invoices, compliance with company purchasing policies and internal controls, and leading a high-performing AP team.

The ideal candidate combines strong operational accounting experience with a continuous-improvement mindset and enjoys building efficient processes that leverage automation. As Mariana continues to grow, this role will play a key part in implementing best-in-class procure-to-pay practices, improving vendor relationships, strengthening internal controls, and supporting the company’s readiness for continued growth.

This role will work closely with Procurement, Operations, Accounting, Treasury, FP&A, and business leaders across multiple operating locations.

What You’ll Do

Accounts Payable Operations

• Supervise and assist in the daily processing of vendor invoices across multiple legal entities.

• Ensure invoices are processed accurately, completely, and in accordance with company policies and payment terms.

• Ensure three-way matching of purchase orders, goods receipts, and vendor invoices.

• Review invoice coding for accuracy, including general ledger accounts, departments, projects, entities, and budget classes.

• Manage invoice queues and ensure service-level expectations for invoice processing are achieved.

• Coordinate weekly payment proposals with Treasury while supporting working-capital objectives and vendor relationships.

• Monitor accounts payable aging and proactively

Vendor Management

• Serve as the primary escalation point for vendor inquiries, account statements, and payment disputes.

• Build strong relationships with key suppliers while ensuring consistent communication regarding payment status.

• Coordinate the resolution of invoice discrepancies with Procurement and operational teams.

• Oversee vendor onboarding documentation, including W-9 or W-8 forms, banking information, tax forms, certificates of insurance, and other required support.

• Prepare and complete vendor credit applications to establish or expand supplier credit terms.

• Assist in maintaining an accurate vendor master and support vendor due-diligence processes.

Invoice Approvals and Exception Management

• Supervise, coach, mentor, and develop Accounts Payable staff.

• Establish performance expectations and monitor individual and team productivity, quality, and timeliness.

• Conduct regular performance reviews and provide ongoing feedback and coaching.

• Develop cross-training plans to ensure operational continuity and appropriate coverage.

• Promote a culture of customer service, accountability, collaboration, and continuous improvement.

Team Leadership

• Supervise, coach, mentor, and develop Accounts Payable staff.

• Establish performance expectations and monitor individual and team productivity, quality, and timeliness.

• Conduct regular performance reviews and provide ongoing feedback and coaching.

• Develop cross-training plans to ensure operational continuity and appropriate coverage.

• Promote a culture of customer service, accountability, collaboration

Process Improvement and Internal Controls

• Identify opportunities to automate invoice processing, approval workflows, and exception handling.

• Support the implementation and optimization of AP automation tools, OCR technologies, and ERP workflows.

• Develop and maintain standard operating procedures, desk procedures, and process documentation.

• Ensure compliance with internal controls, segregation of duties, procurement policies, and payment authorization requirements.

• Support internal and external audit requests and remediation activities.

• Monitor key performance indicators and recommend

Reporting and Analytics

• Prepare and report key Accounts Payable metrics, including:

• Invoice processing cycle time and backlog

• Percentage of invoices supported by purchase orders

• Outstanding approval aging

• Vendor aging

• Non-PO invoice volume

• Provide regular reporting and recommendations to Finance leadership to improve operational efficiency and support decision-making.

Desired Qualifications

• Bachelor’s or Associate’s degree in Accounting, Finance, Business Administration, or a related field

• Five or more years of progressive Accounts Payable experience, including at least two years supervising or leading AP staff

• Experience in manufacturing, mining, energy, industrial, construction, or another asset-intensive industry is preferred

• Strong understanding of procure-to-pay processes, invoice matching, vendor management, and payment controls

• Experience with ERP systems such as Odoo, NetSuite is preferred

• Experience with AP automation platforms and OCR technologies is highly desirable

• Strong knowledge of internal controls, segregation of duties, and financial compliance

• Experience implementing process improvements and automation initiatives

• Excellent organizational skills and the ability to manage competing priorities in a fast-paced environment

• Strong analytical, problem-solving, interpersonal, and communication skills

Our culture is built on three principles:

Extreme Ownership – We take full responsibility for outcomes, relentlessly driving toward solutions.

Engineer Out Requirements, then Automate – We simplify, optimize, and then automate for scale.

Share Your Legos – We collaborate openly, share knowledge, and empower each other to build bigger, better solutions.

Join us as we build the future of responsible mineral sourcing and supply.