How does the timing of income and deductions affect my taxes?

Tax planning often involves shifting income and deductions between years. Deferring a year-end bonus to January keeps income off this year's return. Prepaying January mortgage interest or property taxes in December (if not hitting the SALT cap) pulls deductions forward. Accelerating business expenses before year-end lowers self-employment income. The goal is always to recognize income in a lower-bracket year and deductions in a higher-bracket year.