You need to file a schedule C to report income you earned as self-employed contractor.
Your self-employment taxes will be calculated based on your net business income - use schedule SE - http://www.irs.gov/pub/irs-pdf/f1040sse.pdf - please verify if that schedule is included into your tax return.
The amount of your self-employment taxes will be remitted and reported to Social Security Administration.
The business code "999999" is used when you are not able to find the appropriate code.
See list of codes in instructions for the schedule C page 10 - http://www.irs.gov/pub/irs-pdf/i1040sc.pdf
You might need to use - 485300 Taxi & limousine service.
Let me know if you need any help.
Tax Preparer
Taxes, Immigration, Labor Relations