I am trying to understand how do I calculate the safe harbor for taxes for this year so I do not have to pay penalty when filing taxes for 2024. Apologize if some of the questions are very fundamental and obvious, but I am asking as I am confused.

I am trying to use the safe harbor rule "

*Paid at least 100% of the tax you owed for last year*"

**How do I check what I owed last year?**- I am assuming this is 1040 #24 titled "This is your total tax". Is this correct?

**How do I make sure how much I am withholding in tax this year?**- I am looking at my pay check and calculating what I will be withholding based on the "Federal Taxes" withheld per pay cheque. Is that correct? Do I consider SS, medicare in there or just federal tax?

Again apologize for a silly question, I am myself surprised how I thought I always knew this but turns out when you get into details it gets confusing.

Thanks!