No, you wouldn't have filed it last year -- it's a new schedule that the IRS created.
Schedule 4 is used when you owe other taxes, such as self-employment tax, household employment taxes, additional tax on IRAs or other qualified retirement plans and tax-favored accounts. These were on page 2 of Form 1040 last year.
Please see Schedule 4 to see what's reported there.
NOTE: Schedule 4 is obsolete as of Tax Year 2019. Schedule 2 and the previous Schedule 4 were combined into Schedule 2 in Tax Year 2019.
[Edited 3|16|2020 10:54 am]
