Working Poor

For 1099 wages the amount for social security is 12.4% and another 2.9% for medicare.

For the 2015 tax year, filing due by 15 April 2016, the personal exemption is $4000 and the standard deduction for single is $6300. All income over that sum, $10,300, is subject to federal tax. For example if you had w-2 wages of $20,000, 1099 wages of $10,000, rental income profits of $2,000 and investment profits of $500:

>> You owe 15.3% on the $10,000 in 1099 wages = $1,530 (the portion for the w-2 wages of $20,000, should have been withheld and paid by your employer. You'll should plan to pay the remaining $1,530)
>> Your total income is $32,500. Subtract the exemption and standard deduction that leaves $22,200 subject to federal tax. (The federal tax on the whole amount is about $2,700. The portion from w-2 wages should have been withheld and paid by your employer. You'll need to pay the rest. Check your last pay stub for the amounts already paid.)

Just a thought; if you're already collecting on your social security and your only income is from 1099 wages, I believe any additional wages you earn will never increase the amount of social security you receive. If that's the case and your client is willing, forming a private corp and taking your earnings as business profits rather than wages will save you the 15.3%. All that could change based on state and local tax laws. YMMV so check with a tax pro.