On November 1, 2021, the IRS published Publication 1167, General Rules and Specifications for Substitute Forms and Schedules. This updated publication is dated October 25, 2021. Although there have not been any major updates, notice a number of editorial changes that eliminate repetitive information throughout the publication.
Check out the October 2021 Revision of Pub. 1167 here: https://www.irs.gov/pub/irs-pdf/p1167.pdf