Why do I have a tax liability charge? Turbo Tax told me last year to pay quarterly tax payments but my income substantially decreased in 2021 so I did not pay.

[Bsch4477]

Your tax owed was greater than estimated tax paid. If you are self employed you have to pay self employment tax even if your regular income tax is zero. 

[LeonardS · Accepted solution]

From your post, it appears that you were required to pay estimated taxes although your income decreased substantially.  The U.S. tax system operates as a pay-as-you-go system. What this means is that you must pay your taxes as they occur or you will be assessed an underpayment penalty.  

@pam35337