AP Accountant

MISSION Mirum Pharmaceuticals is a biopharmaceutical company dedicated to transforming the treatment of rare diseases. We are passionate about advancing scientific discoveries to become important medicines for rare disease patients. We are collaborative, creative, and experienced professionals and we’re looking to augment our team with other individuals who embody our values: care, be real, get it done, and have fun, seriously. POSITION SUMMARY We are seeking a detail-oriented and highly organized AP Accountant to join our Accounting Operations team. This role is responsible for the accurate and timely processing of accounts payable transactions, expense reports, vendor communications, and related general accounting activities. The ideal candidate will thrive in a dynamic, complex, and fast-paced environment and possess strong analytical, organizational, customer service and critical thinking skills. This position requires a combination of technical accounting knowledge and operational experience, along with the ability to independently resolve issues, manage multiple priorities, and collaborate effectively across departments. The candidate should be able self-motivated, adaptable, and a strong team player with a solid work ethic. This role regularly interfaces with internal stakeholders and external vendors and plays a critical role in supporting the Finance and Accounting organization within a growing company. JOB FUNCTIONS/RESPONSIBILITIES Responsible for processing high volumes of accounts payable transactions, including invoice entry, account coding, and ensuring proper accounting period entry for accuracy and compliance with company policies. Review invoices for appropriate supporting documentation prior to processing and payment. Process accounts payable by matching invoices with appropriate purchase orders and supporting documentation. Review vendor contracts and exercise judgment in assigning appropriate expense accounts, departments, and project coding for non-PO invoices. Research and resolve vendor account, invoice, and payment discrepancies while maintaining accounts payable in good standing. Manage and monitor the AP email inbox, including responding to vendor inquiries, payment requests, and invoice related questions. Ensure adherence to company signature authority and approval policies. Manage the Concur expense reporting system, including expense report processing, audits and user support. Review employee expense reports thoroughly to ensure compliance with company policies and procedures. Review expense reports containing Healthcare Professional (HCP) related expenses to ensure Sunshine Act compliance. Manage the expense reports email inbox and provide support for employee expense submissions and travel booking inquiries. Provide excellent customer service to internal stakeholders and external vendors. Support quarterly reviews and annual audit by providing requested documentation to auditors. System maintenance for tax reporting compliance and year-end processing of 1099’s. Support financial systems implementations and participate in process improvements. Assist on special projects and ad-hoc assignments as needed. Adapt to evolving responsibilities and business needs within a growing organization. QUALIFICATIONS Education /Experience: Bachelor’s degree in Accounting, Finance, or related field preferred. 5+ years of Accounts Payable or general accounting experience, preferably in a high-volume environment. Required experience with Concur expense management system and NetSuite ERP system. Strong understanding of AP processes, expense reporting, and internal controls. Knowledge of 1099 reporting requirements and audit support processes. Proficient in Microsoft Office applications, particularly Excel. Familiarity with Sunshine Act compliance is preferred. Knowledge, Skills and Abilities: Strong analytical, problem solving, and critical thinking skills with the ability to exercise sound judgment. Strong verbal a