Does the term "tax liability" include social security and medicare?

[streampaw]

Let's say a self-employed single person with one dependent made about 11k in 2018, filed a tax return as single, and claimed one child. Their form 1040 only shows line 14, which is "other taxes", and it was around $1600 which are self-employment taxes. Line 11 shows 0, so does that mean they had no "tax liability in 2018"? They also got EIC of around $3000, so they actually received a refund for 2018. 

Let's say in 2019 they are probably going to make 70k-100k (but still unsure exactly how much, as income fluctuates, but definitely more than in 2018). Do they need to make estimated quarterly payments? It says if there was no tax liability in the previous year, then the estimated quarterly payments are not required. Does self-employment tax count as a "tax liability"? 

[SweetieJean]

Are you a tax preparer? You have asked a number of "let's say" questions on this Board.

[streampaw]

No, I just don't want to give out personal info

[fanfare]

SE tax will be added to your tax due, as will any other income tax surcharges, like AMT, etc.

You must take that into account when estimating your quarterly "Estimated Tax" payments.

[fanfare]

How else can I explain it?
If this doesn't answer your question, please rephrase your question.

[streampaw]

Basically I am trying to figure out if a self-employed person is exempt from paying and filing quarterly taxes in 2019. If they made only 11k in 2018 and got a tax refund (line 14 on 1040 was $1600 which was self employment tax, but they got EIC so they got a refund). Line 11 was 0. A condition for being exempt from filing and paying quarterly taxes in 2019 is if there was no "tax liability in 2018". So I'm trying to figure out what "tax liability means" to find out whether or not this person is exempt from filing and paying quarterly taxes in 2019.

[VolvoGirl]

Well even if not required you better send in some estimates so you don't owe it all on your tax return.  Unless you have a lot of expenses to reduce the profit.

[streampaw]

So it's not required i guess?

[VolvoGirl]

You must make quarterly estimated tax payments for the current tax year if both of the following apply:
- 1. You expect to owe at least $1,000 in tax for the current tax year, after subtracting your withholding and credits.
 
- 2. You expect your withholding and credits to be less than the smaller of:
    90% of the tax to be shown on your current year’s tax return, or
  100% of the tax shown on your prior year’s tax return. (Your prior year tax return must cover all 12 months).

See 1040ES Instructions
<a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/f1040es.pdf">https://www.irs.gov/pub/irs-pdf/f1040es.pdf</a>

IRS info on Underpayment Penalties..
<a rel="nofollow" target="_blank" href="http://www.irs.gov/taxtopics/tc306.html#skiptocontent">http://www.irs.gov/taxtopics/tc306.html#skipt...>

[Zbucklyo]

It is never required.  The worst that can happen is that you will be charged an underpayment penalty, and of course, might have a very large balance due come April 15th, 2020.

[streampaw]

So I am trying to avoid an underpayment penalty. That's what I'm trying to figure out, what does the second part mean about the 90% and 100%?

[VolvoGirl]

Let me add this to the conversation.  I had a refund once and still had a penalty for not paying in evenly during the year.