@ ambitionz1993 wrote:
Does that make sense or does it make more sense to amend my personal tax returns?
You cannot simply elect to file your businesses as an S corporation; there is a formal procedure you need to follow, starting with filing Form 2553 (link below).
If the error you made was not including the income/expenses from your businesses on your personal income tax returns, then all you need to do is amend to include Schedule C (your single-member LLC is disregarded for federal income tax purposes).
https://www.irs.gov/instructions/i2553
