Senior Billing Specialist

Founded in 1989 and headquartered in Reston, Virginia, SOSi is a private defense and government solutions business specializing in advanced technology systems and mission support. Its capabilities include data science, software development, network engineering, intelligence, surveillance, and reconnaissance (ISR), and logistics. SOSi is seeking a detail-oriented and proactive Senior Billing Specialist to become a key member of our finance team. In this role, you’ll own critical billing and accounts receivable functions that keep our operations running smoothly and efficiently. If you enjoy solving problems, improving processes, and working in a collaborative environment where your work truly matters—this is the opportunity for you. What You’ll Do As a Senior Billing Specialist, you’ll play a vital role in ensuring accurate and efficient financial operations. Your responsibilities will include: Creating and delivering accurate, timely invoices based on contract terms and services provided. Reconciling billed and unbilled receivables against the general ledger. Managing contract close-outs, including final variance analysis and contract release. Monitoring accounts receivable to ensure prompt collection and resolution of outstanding invoices. Serving as a trusted point of contact for customers, resolving billing questions and discrepancies with professionalism. Supporting and mentoring junior team members, helping elevate team performance. Processing payments, applying transactions, and resolving account discrepancies. Maintaining accurate billing records and customer accounts. Preparing and sharing reports on billing and AR performance with leadership. Ensuring compliance with company policies and industry standards. Identifying opportunities to streamline processes and improve accuracy. Collaborating cross-functionally with finance, sales, and other teams to achieve business goals. What You Bring We’re looking for someone who combines strong technical skills with a collaborative and customer-focused mindset: Bachelor’s degree in Accounting, Finance, Business, or related field, or equivalent experience. Seven+ years of experience in billing, accounts receivable, or similar finance roles. Experience with ERP systems such as Deltek Costpoint. Advanced Excel skills (e.g., PivotTables, VLOOKUPs, complex reporting). Strong proficiency with accounting systems and Microsoft Excel. Exceptional attention to detail and accuracy. Excellent communication skills and the ability to build positive relationships internally and externally. Strong problem-solving and analytical skills. Ability to manage multiple priorities and meet deadlines in a fast-paced environment. A high level of integrity and professionalism when handling sensitive financial data. A customer-first attitude and commitment to service excellence. Work Environment Standard office setting with a hybrid schedule with 2 days in office and 3 days of remote work. A collaborative and supportive team environment. Opportunities for career growth and development. The chance to make a meaningful impact on the organization’s financial success. Occasional extended hours or weekends may be required during peak periods. Why SOSi? At SOSi, your work is valued, your growth is supported, and your contributions make a real difference. We foster a culture of teamwork, accountability, and continuous improvement—empowering you to do your best work every day. Working at SOSi All interested individuals will receive consideration and will not be discriminated against for any reason.