Retirement turns tax planning from a deduction exercise into a withdrawal-sequencing exercise.
During working years, planning is mostly about reducing taxable income. In retirement, it is about choosing where each dollar of spending comes from.
The order of withdrawals across taxable, tax-deferred, and tax-free accounts changes the lifetime bill substantially, and the right order changes as brackets and required distributions shift.
Conversions in low-income years are the other main lever, and the window for them is usually narrower than people expect.