If you are new to being self employed, are not incorporated or in a partnership  and  are acting as your own bookkeeper and tax preparer you need to get educated ....  

If you have net self employment income of $400 or more you have to file a schedule C in your personal 1040 return for self employment business income. You may get a 1099-NEC  for some of your income but you need to report all your income.  So you need to keep your own good records. Here is some reading material……

IRS information on Self Employment….
http://www.irs.gov/Businesses/Small-Businesses-&-Self-Employed/Self-Employed-Individuals-Tax-Center 

Publication 334, Tax Guide for Small Business
http://www.irs.gov/pub/irs-pdf/p334.pdf 

Publication 535 Business Expenses
http://www.irs.gov/pub/irs-pdf/p535.pdf 

Publication 463 Travel, Gift, and Car Expenses

Https://www.irs.gov/pub/irs-pdf/p463.pdf  

Home Office Expenses … Business Use of the Home

https://www.irs.gov/businesses/small-businesses-self-employed/home-office-deduction

https://www.irs.gov/pub/irs-pdf/p587.pdf

Publication 946 … Depreciation

https://www.irs.gov/pub/irs-pdf/p946.pdf

                                              

There is also QuickBooks Self Employment bundle you can check out which includes one Turbo Tax Self Employed return and will help you keep up in your bookkeeping all year along with calculating the estimated payments needed ....
http://quickbooks.intuit.com/self-employed

Self Employment tax (Scheduled SE) is generated if a person has $400 or more of net profit from self-employment on Schedule C.  You pay 15.3% for 2017 SE tax on 92.35% of your Net Profit greater than $400.  The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare.  So you get social security credit for it when you retire.  You do get to take off the 50% ER portion of the SE tax as an adjustment on line 27 of the 1040.  The SE tax is already included in your tax due or reduced your refund.  It is on the 1040 line 57.  The SE tax is in addition to your regular income tax on the net profit.
 


PAYING ESTIMATES
For SE self employment tax - if you have a net profit (after expenses) of $400 or more you will pay 15.3% for 2017  SE Tax on 92.35% of your net profit in addition to your regular income tax on it. So if you have other income like W2 income your extra business income might put you into a higher tax bracket.

You must make quarterly estimated tax payments for the current tax year (or next 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.)

To prepare estimates for next year, You can just type W4 in the search box at the top of your return , click on Find. Then Click on Jump To and it will take you to the estimated tax payments section. Say no to changing your W-4 and the next screen will start the estimated taxes section.

OR Go to….
Federal Taxes or Personal (H&B version)
Other Tax Situations
Other Tax Forms
Form W-4 and Estimated Taxes - Click the Start or Update button

How does my side job affect my taxes?

You’re considered self-employed—even if it’s just something you do on the side, like drive for Uber, babysit, or blog.

Your taxes are handled differently than when you’re an employee of a company.

As a self-employed individual you:

• will pay self-employment tax (because income tax and Social Security aren’t deducted from your pay)
• will get a 1099-MISC or 1099-K (unless you only accept cash or personal checks)
• file a Schedule C, Form 1040 (this is how you report business expense or loss of income)
• can deduct money you spent on work-related expenses (like mileage, home office expenses, and cell phone use)
• can estimate the taxes that are due and make quarterly estimated tax payments during the year

Get started by entering your income from self-employment. We’ll handle the rest, from creating the forms you need to reviewing work-related expenses that can help reduce your taxes.

Related Information:

• Where do I enter Schedule C?
• What self-employed expenses can I deduct?
• What is the self-employment tax?
• What is this new 20% business deduction?

Here’s a short answer for you.

You file one tax return for the entire year that reports your business income along with any other personal income such as prizes or regular wages or investment income, plus your personal deductions, dependents, and credits.  If you are self-employed, your tax return will include a form called schedule C which reports your business income and deducts your business expenses.  The net profit from the business is your taxable business income, and that flows to the rest of form 1040 where it is combined with your other income and deduction information.

however, you may be required to pay estimated taxes four times a year based on your estimated business income. The tax system is supposed to be pay as you go.  This is usually accomplished by wage withholding. When you are self-employed, you generally have to make an estimated tax payment four times a year based on your income earned during that quarter.  If you pay too little in estimated taxes, you will owe more tax at the end of the year when you file your official form 1040. If you pay extra estimated taxes, you will get that back as a refund when you file your tax return.

The quarters are:

Estimated payment due April 15 for income earned between January and March.

Estimated payment due June 15 for income earned in April and May. 
Estimated payment due September 15 for income earned June, July and August.

Estimated payment due January 15 for income earned between September and December.

The quarters are not uniform three months each as you will see, that was not a mistake on my part.

Once you determine the correct amount to pay in estimated taxes, the best way to pay electronically is at the IRS website, www.irs.gov/payments. If you pay online, the payment is linked to your Social Security number and you don’t need to send in any paper forms.

don’t forget that you may also owe state income tax payments on a quarterly basis.

TurboTax is only designed to prepare your final tax return at the end of the year and does not have a function to recommend an estimated payment based on your ongoing business activities. That function is contained in business software such as QuickBooks or Mint, or you may track your income and expenses on paper or using other software.

The longer answer above contains many links to further information on how to keep proper records and how to calculate your estimated taxes.