The full US stack in one calendar
US compliance is a stack, not a single return: federal, state, payroll and sales tax each run on their own deadlines, and a missed state filing can trigger a franchise tax even with no activity. We set every deadline at the start of the year so nothing is discovered late.
Foreign-owned US subsidiaries face additional reporting — Form 5472, the related-party transactions statement, and the 1120-F where relevant. We file these alongside the 1120 so the US entity's cross-border position is complete.