Should I do Roth conversions or keep income low for ACA subsidies when I retire early?

This is one of the central tensions of early retirement, and there is no universal answer. Roth conversions done in low-income years lock in low tax rates and reduce future required minimum distributions, but every dollar converted raises your MAGI and can reduce your ACA premium tax credits, effectively adding a hidden 'tax' in the form of lost subsidy. If your traditional balances are large and future RMDs threaten to push you into high brackets, aggressive conversions may win despite the lost subsidies. If your traditional balances are modest and healthcare is a big line item, prioritizing subsidies may save more today. Many retirees do partial conversions, or concentrate conversions in the years after 65 when they are on Medicare and subsidies no longer apply. Run both paths yearly; the subsidy and bracket thresholds change annually per the IRS and marketplace.