Many tax rules are based on adjusted gross income, which is not taxable (after deductions) income.

Itemized deductions only matter if, in total, they exceed the standard deduction.

Some income sources get preferential treatment (qualified dividends and long-term capital gains).

A dollar of extra income can trigger many dollars of tax on social security benefits, higher medicare premiums, and loss of Affordable Care Act subsidies.

Net Investment Income tax @3.8%

RMDs force income to be recognized and taxed even if not needed or spent.

Tax planning, as opposed to tax preparation, which arranges and adjusts your finances to minimize the lifetime taxes you pay, can save you thousands of dollars.