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You are not required to register your self employment but you will need to estimate what your taxes will be for the coming year so you can look to making Estimated Tax payments
As a self-employed individual, generally you are required to file an annual return and pay estimated tax quarterly.
Self-employed individuals generally must pay self-employment tax (SE tax) as well as income tax
. SE tax is a Social Security and Medicare
tax primarily for individuals who work for themselves. It is similar to the Social Security and Medicare taxes withheld from the pay of most wage earners. In general, anytime the wording "self-employment tax" is used, it only refers to Social Security and Medicare taxes and not any other tax (like income tax).
Estimated tax is the method used to pay Social Security and Medicare taxes and income tax, because you do not have an employer withholding
these taxes for you. Form 1040-ES, Estimated Tax for Individuals (PDF), is used to figure these taxes. Form 1040-ES contains a worksheet that is similar to Form 1040.
You will be reporting this income using Schedule C which is attached to your 1040 return.
I would not think you would need to advise your employer but that is more of an employment question then a tax question.
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