Self employed

For Line 2a the worksheet is referring to if you are going to take the Standard Deduction or Itemized Deductions.  If you are Single the Standard Deduction is $12,200 for 2019, for Head of Household it is $18,350 and for Married Filing Joint it is $24,400.

If you have Mortgage Interest, Property Taxes, State Income Tax Paid, Medical Expenses and Charitable Contributions that are greater than your Standard Deduction then you would subtract that amount from Line 1.  Remember that State Income Tax Paid and Property Taxes are limited to a deduction of $10,000.

Line 7a are Credits that you may qualify for including:

• Foreign tax credit. Attach Form 1116
• Credit for child and dependent care expenses. Attach Form 2441
• Education credits from Form 8863,
• Retirement savings contributions credit. Attach Form 8880
• Residential energy credits. Attach Form 5695
•  

Line 10 refer to additional taxes such as:

• Self-employment tax. Attach Schedule SE
• Unreported social security and Medicare tax from: Form a 4137 or 8919
• Additional tax on IRAs, other qualified retirement plans, and other tax-favored accounts. Attach Form 5329
• Household employment taxes. Attach Schedule H
• Repayment of first-time homebuyer credit from Form 5405.
• Health care: individual responsibility
•  

On Line 11b yes, you can claim $4,000 for Child Tax Credit if both of your children are under the age of 17 years old.

Since you have not made any estimated payments for 2019 you can prepare your tax return and see the amount that will be due.  To make estimated payments for 2020 you can take the amount you owed for 2019 and divide that by 4 to make the estimated payments due for 2020.  If you believe your overall income will be greater TurboTax allows you to enter the increase in income and will calculate the additional tax due when preparing your estimated payments for 2020.

Link for more information about Estimated Taxes

It is best for you to make estimated payments online at

Link to make estimated payments on IRS web site