TurboTax software can only be used to prepare returns for the tax year it was bought for, as it only has the tax forms for one tax year. If you have bought 20 returns for 2018, that means you can prepare 20 returns for the 2018 tax year. You would not be able to use the software for any past or future years. You would have to purchase the software for 2019 to create tax returns for 2019, and the same goes for 2020.