Accounting Operations Associate

About Mainstay

Mainstay is the leading market intelligence platform purpose built for buying, managing, and selling homes in the single family rental industry. As an AI native company, we turn complex data into clarity that helps the industry move forward with confidence. Founded within Opendoor, Mainstay launched as an independent company in 2024 and recently raised a Series A round led by Khosla Ventures.

Ready to shape the future of real estate with AI? Join Mainstay and help us redefine what's possible in the single family rental space. If you thrive on solving complex problems and want to make a tangible impact in a fast-growing industry, we'd love to hear from you - apply now and let's move the industry forward, together!

Role Overview

Mainstay is hiring an Accounting Operations Associate to support the various operational aspects of our finance and accounting team as we scale. You'll oversee AP, AR, spend management systems, daily treasury functions, support close, and ensure GL data integrity.

What You'll Do

Accounts Payable & Receivable (primary focus)

• Own the full AP cycle: process vendor invoices, verify coding and approvals, manage payment runs, and maintain vendor terms.
• Own the full AR cycle: generate and send customer invoices, track collections, manage past-due follow-up, and apply cash receipts.
• Maintain accurate AP/AR aging schedules; proactively flag risk and resolve discrepancies with vendors and customers.
• Track and report on AP/AR KPIs (e.g., DPO, DSO, aging trends) and use them to drive process improvement.
• Own vendor onboarding, W-9/W-8 collection, and vendor record maintenance.
• Serve as the go-to point of contact for all AP/AR questions from vendors, customers, and internal teams.

Treasury & Cash Management

• Monitor daily cash positions across Mainstay's bank and operating accounts.
• Process and execute wire transfers, ACH payments, and other cash movements in line with internal controls and approval limits.
• Manage day-to-day banking relationships and administer online banking platforms - user access, permissions, and alerts.
• Support short-term cash flow forecasting and proactively flag liquidity needs to the Controller.
• Reconcile treasury and bank accounts, and investigate/resolve discrepancies.

Financial & Accounting Systems Ownership

• Act as the primary owner/administrator of Mainstay's accounting, AP/AR, and treasury/banking platforms (e.g., ERP, Bill.com, banking portals) - user access, configuration, and troubleshooting.
• Manage integrations across systems (AP/AR, banking, general ledger, payroll), ensuring data flows cleanly and stays reconciled.
• Own system maintenance: software updates, permissions audits, and ongoing troubleshooting across the financial systems stack.
• Evaluate, recommend, and help implement new or upgraded financial systems and automation as the company scales.
• Build and maintain documentation/SOPs for financial systems and workflows.

Month-End Close & Reconciliations

• Prepare journal entries and support the monthly close checklist.
• Reconcile bank and credit card accounts, and research/clear variances.
• Maintain supporting schedules for prepaids, accruals, and other balance sheet accounts.

Financial Reporting & Light FP&A

• Assist in preparing monthly financial reports and management summaries.
• Support budget-to-actual tracking and basic variance analysis.
• Pull and organize data for ad hoc financial requests.

Payroll & Expense Management

• Support payroll processing in partnership with the Controller/HR.
• Review and process employee expense reports and reimbursements.
• Help maintain compliance with expense policy and documentation standards.

What You'll Bring

• 1-3 years of experience in accounting, bookkeeping, or a related finance role, with meaningful hands-on AP/AR experience.
• Exposure to treasury or cash management tasks (bank transfers, cash positioning, reconciliations) - direct treasury experience is a strong plus, not a requirement.
• Experience administering or power-using financial systems (e.g., an ERP, AP/AR platform, or banking portal) - comfortable owning a system, not just using it.
• Strong Excel/spreadsheet skills and comfort working across multiple financial systems.
• Strong attention to detail and follow-through on recurring, deadline-driven, controls-sensitive work.
• Clear communicator, comfortable working with vendors, customers, banks, and internal teams.
• A systems/process mindset - someone who naturally looks for ways to make financial operations more accurate and efficient.
• Interest in growing beyond AP/AR into broader accounting, treasury, and finance operations.
• No certification required; degree in accounting, finance, or related field preferred but not mandatory.

Nice to Have

• Experience at a startup or fast-growing company.
• Prior exposure to treasury management systems or online banking platforms.
• Prior experience owning/administering a financial system beyond AP/AR (e.g., ERP, payroll, or expense tools).
• Familiarity with payroll systems and expense management tools.

Mainstay Built on Trust

At Mainstay, trust is at the core of everything we do. We build trust with everyone -- from candidates to employees to partners. We believe in fairness and openness throughout our hiring process, evaluating candidates based on qualifications without regard to race, color, religion, national origin, age, gender, marital status, disability, veteran status, sexual orientation, gender identity, or any other protected status. Our privacy practices describe how we handle applicant information, you can find the policy details for California residents here.

We are committed to providing reasonable accommodations throughout our recruitment processes for candidates with disabilities, pregnancy, religious beliefs, or other reasons protected by applicable laws. If you require assistance or a reasonable accommodation, please contact us at View email address on click.appcast.io