Tax Manager/Senior Tax Manager

Old Mission is a global proprietary trading firm that leverages state-of-the-art technology and research to identify and execute profitable trading strategies across multiple asset classes around the world. Our offices in Chicago, New York, and London are all composed of naturally-curious individuals who thrive in a team environment and constantly strive for improvement. Old Mission does not seek capital from outside investors, allowing us the flexibility to aggressively invest in our team members and keep them engaged in the firm’s growth. About the position This is a hands-on role in every sense. The Tax Manager works alongside the Tax Director, not behind them. Both positions are expected to work together: preparing workpapers, reviewing returns, conducting primary research, owning compliance deadlines, and building the analysis that informs the firm’s tax positions. Responsibilities U.S. International Tax Prepare and own U.S. international tax compliance workpapers and supporting schedules across the firm's controlled foreign corporations and partnerships, including GILTI/NCTI, FDII/FDDEI, BEAT, Subpart F, foreign tax credits and FTC limitation analysis, and foreign withholding and treaty positions Maintain and update CFC and partnership analyses including tested income, tested loss, net deemed tangible income return calculations, and high-tax exclusion evaluations; coordinate with external advisors on FTC planning and transfer pricing strategies Monitor the impact of OBBBA, evolving IRS guidance, and OECD Pillar Two developments on the firm's international tax positions and assess implications for compliance and planning Support transfer pricing documentation and intercompany agreements for cross-border transactions between U.S. and foreign entities. Federal, State & Local Tax Compliance Prepare tax return information packages and detailed workpapers for external tax consulting firms; independently review all externally prepared federal and state returns prior to submission Support preparation and review of indirect tax filings including VAT, Use Tax, and GST across applicable domestic and international jurisdictions Own withholding and information reporting obligations for Forms 1099, 1042-S, and 8804 for the firm and its related entities Build and maintain the firm’s tax compliance calendar; proactively identify all upcoming deadlines and coordinate timely completion with internal teams and outside advisors Research, Planning & Authority Response Conduct primary research on federal, state and local, and international tax issues; prepare well-reasoned technical memos for Tax Director review Prepare substantive responses to information document requests (IDRs) from the IRS, state, and city taxing authorities; maintain organized examination support files Monitor and assess legislative and regulatory developments including IRS guidance, Treasury regulations, and OECD Pillar Two updates; brief the Tax Director on implications for the firm Provide tax analysis in support of proposed transactions, new entity structures, and strategic initiatives Process, Data & Technology Identify and implement process improvements to tax workflows; evaluate new tools and procedures for more accurate, efficient compliance Leverage Excel (Power Query, XLOOKUP, PivotTables, array formulas) and AI research tools to streamline workpaper preparation, data manipulation, and reconciliation Document and maintain policies, procedures, and internal controls for the Tax function Work cross-functionally with Accounting, Legal, and Operations on tax matters, regulatory reporting, and ad hoc special projects as directed Required Skills 6–8+ years of tax experience; public accounting background at the Manager or experienced Senior level strongly preferred (Big 4, national firm, or strong regional with FS practice) Genuine hands-on technical depth in U.S. and international tax, direct experience preparing and reviewing GILTI/NCTI, Subpart F, and foreign tax…