There is no registration requirement to operate in the state of Pennsylvania as a sole proprietor. You can use your social security number for Federal and State of Pennsylvania tax filing requirements. However, you must file for a Federal Tax Identification number and a State Tax Identification number if you pay wages and are required to file payroll tax returns. This can be done in both cases over the Internet. Registering does not decrease tax liabilities in any way.
You may deduct certain automobile expenses associated with moonlighting income. The deductibility of these expenses is not dependent on any kind of registration. If you would like to discuss the deductibility of certain expenses as a sole proprietor please contact me at 412-343-8050. I would be more than happy to assist you with this or any other tax issue. Thanks.

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