When do I pay taxes if I'm self employed?
I strongly recommend that you talk to an accountant right away because you could save some money by making a tax payment by January 15, 2014. You will receive Forms 1099-MISC from the various entities with whom you are doing business as a contractor detailing how much money they paid you. A copy will go to the IRS also. You file a Schedule C with your Form 1040 in which you detail how much you received on the 1099-MISC forms as well as any other income that your contracting business received (e.g. amounts less than $600 for which a 1099-MISc does not need to be issued, or tips, say, if you are a taxi-driver running your own cab), and you can deduct various expenses that you incurred in generating this income, including tools, books, (or gasoline!) etc that you bought for doing the job. You will need to file a Schedule SE that will compute how much you owe in Social Security and Medicare taxes on the net income on Schedule C. You will pay at twice the rate that employees pay because you get to pay not only the employee's share but also the employer's share. At least, you will not have to pay income tax on the employer's share. Your net income on Schedule C will transfer onto Form 1040 where you will compute how much income tax you owe, and then add on the Social Security tax etc to compute a final amount of tax to be paid. You will have to pay a penalty for not making tax payments every quarter during 2013, plus  interest on the tax paid late.  Send the IRS a check for the total. If you talk to an accountant right away, he/she will likely be able to come up with a rough estimate of what you might owe, and sending in that amount by January 15 will save some money. The accountant can also help you set up for the 2014 tax year during which you could make quarterly payments of estimated tax for 2014 and avoid the penalties and interest referred to above.
You can file a revised W-4 with your employer claiming more allowances than you do now. More allowances means less Federal tax and (if applicable and likely with a separate form) less state tax. This doesn't affect social security and Medicare with holding, though.  That being said, US taxes are on a pay-as-you-go system. If the IRS determines that you're claiming more allowances than you're eligible for and not paying the proper taxes throughout the year, they will hit you with an underpayment penalty fee, which would likely negate the benefits of keeping that money in the first place. This is why independent contractors and self-employed people pay quarterly or estimated taxes. Depending on the employer, they may require proof of the allowances for adjustment before they accept the revised W-4. No. An employer is legally obliged to deduct taxes from your pay cheque and send them to the IRS. The only way round that is to either provide evidence of deductions that would reduce your tax bill to nothing, or to become self-employed. Yes if you do it as a hobby, as it's still income. But it should be something you can offset against tax Either way, you shouldn't be doing this as you, you should either register as self employed or create a company. You register this income as self-employed income (or income of the company) and offset the expenses of running the server against tax. In the UK, companies (or self employed people, which are basically companies) pay tax on profit not income (unless VAT applies, in which case they're basically just passing the VAT on for their customers). Since you're not making a profit over the whole year (even if some months are profitable) you will pay no tax. HMRC may or may not find out about it; the risks and penalties involved if they do find out make it unwise not to just declare it and pay the tax on it. Based on the fact you asked the question, I am assuming that you currently pay all your tax through PAYE and don't do a tax return. You would need to register for Self Assessment and complete a return; this is not at all difficult if your tax situation is straightforward, which it sounds like yours is. Then you would owe the tax on the additional money, at whatever applicable rate (which depends on how much you earn in your main job, the rate tables are here: https://www.gov.uk/income-tax-rates/current-rates-and-allowances ). If it truly is a one off you could simply declare it on your return as other income, but if it is more than that then you would need to look at setting up as Self Employed - there is some good advice on the differences here: http://www.brighton-accountants.com/blog/tax-self-employment-still-employed/ :  Broadly, you are likely to be running a business if you have a regular, organised activity with a profit motive, which continues for at least a few months. If the work is one-off, or very occasional (say, a few times per year), or not very organised, or of very low value (say, under £2,000 per year), then it might qualify as casual income. If you think it is beyond the definition of casual income then you would also need to pay National Insurance, as described in the previous link, but otherwise the tax treatment would be the same. I would talk to your HMRC tax office they do have guidance on this issue here  http://www.hmrc.gov.uk/working/intro/employed-selfemployed.htm "One way to do these sorts of calculations is to use the spreadsheet version of IRS form 1040 available here.  This is provided by a private individual and is not an official IRS tool, but in practice it is usually accurate enough for these purposes.  You may have to spend some time figuring out where to enter the info.  However, if you enter your self-employment income on Schedule C, this spreadsheet will calculate the self-employment tax as well as the income tax.  An advantage is that it is the full 1040, so you can also select the standard deduction and the number of exemptions you are entitled to, enter ordinary W-2 income, even capital gains, etc. Of course you can also make use of other tax software to do this, but in my experience the ""Excel 1040"" is more convenient, as most websites and tax-prep software tend to be structured in a linear fashion and are more cumbersome to update in an ad-hoc way for purposes like tax estimation.  You can do whatever works for you, but I would recommend taking a look at the Excel 1040.  It is a surprisingly useful tool." You will be categorized as self employed. Will I have to register myself as a company or can go on unregistered and work You can register a company or can use an umbrella company or work as a sole trader. Remember as a sole trader you are legally responsible for you company's activities, an if a company sues you for your work he can take compensation from your personal assets. As a company your liability ends with the company, if your company is sued. Your personal assets are outside the purview of the lawsuit, but the court can attach that also but those are rare. This doesn't matter if you use an umbrella company. If you intend to be doing this for a short time(maybe a year or so), go for an umbrella company. Else register a company. will take you 5 minutes to form one. Depending on your earning you might need to register for VAT too. A comprehensive guide for self employed on HMRC. what would i need to be sound in uk and to be fit to work online as a freelancer? The same as above. Will it include paying any tax or paying any insurance Yes you have register for National Insurance(NI), before you can pay yourself a salary. The benefit of a company is you pay yourself a minimum salary, below the limit above which you have to contribute for NI, and take the rest as dividends. And pay no tax on it, till you don't exceed the limits. When the money comes in my account, will i be accountable to government of uk, to tell the source of income? If you are operating through a company, yes you would need to show your income(including source) and expenditure when you do your annual returns. What should i be knowing, like health insurance and things that are necessities in uk for a freelancer ? No health insurance as NHS exists. You can take out health insurance if you don't want to get into queues in NHS. What you need to do is register as a sole trader. This will automatically register you for self assessment so you don't have to do that separately. For a simple business like you describe that's it.  Completing your self assessment will take care of all your income tax and national insurance obligations (although as mentioned in your previous question there shouldn't be any NI to pay if you're only making £600 or so a year).