The nonbusiness energy credit, which is for adding insulation and certain other energy improvements to a principal residence, has been extended through 2020. The credit for solar and certain other renewable energy added to a principal residence or vacation home applies for 2020, 2021 and 2022 at the rate of 26% (it was 30% prior to 2020). The credit will be 22% in 2023, but zero thereafter unless Congress extends it.
Shifting income to a later year, such as where you defer taxable interest to the following year by purchasing a T-bill or savings certificate maturing after the end of the current year. Investments in qualified retirement plans provide tax deferral.