How were self employed folk taxed in the U.K. before 1997
"This link:  http://www.ifs.org.uk/fs/articles/ewgm_feb93.pdf (from 1996, describing the proposals for the change) seems to answer the question in its description of ""the current system"" - they had to file business accounts and it was calculated by the Inland Revenue from that."
You may also want to consider Delaware and Nevada as possible corporate homes.  They are common choices for out of state corporations.  You may find that they are better options.   Will earnings prior to forming the LLC have to be claimed as self-employment income? If so, would it be easier to wait until the next calendar year to form the LLC? Earnings after forming the Limited Liability Corporation (LLC) will probably have to be claimed as self-employment income.  See How LLC Members Are Taxed for more discussion.  In particular, read the section on self-employment taxes:   The current rule is that any owner who works in or helps manage the business must pay this tax on his or her distributive share (rightful share of profits). However, owners who are not active in the LLC -- that is, those who have merely invested money but don't provide services or make management decisions for the LLC -- may be exempt from paying self-employment taxes on their share of profits. The regulations in this area are a bit complicated, but if you actively manage or work in your LLC, you can expect to pay self-employment tax on all LLC profits allocated to you. As I read it, you actively work in the LLC, so it is unlikely that you can avoid paying self-employment taxes.  So it shouldn't make any difference when you officially start an LLC.  You'll have to pay self-employment taxes before and after creating the LLC regardless.   If you don't want to pay self-employment taxes, you may want to consider forming a Subchapter C corporation.  They don't have the same tax structure as Subchapter S corporations or LLCs.  You would be paid some kind of wage, salary, or commission and the corporation would pay the employer's side of the payroll taxes.   Note that Subchapter S corporations and LLCs exist because they usually pay less in tax than Subchapter C corporations do.  Even including the self-employment taxes that you owe.   A CPA should be able to guide you in making these decisions and help you with setup.   The one time that I started a corporation, I just paid a few hundred dollars to a service and they filed the paperwork for me.  That included state fees and notice costs.  The CPA probably has a service association already. 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. First, request that you complete a tax return. On this tax return, you will complete both the employed and self employed sections. This will give you a total income and tax liability. You will already have paid some tax via PAYE, but you will have to pay additional tax for any other income. For future years there is the option, depending on amount, to collect extra tax through PAYE to cover the other earnings. If it is likely to be the same for the next few years, this may be a better option than paying a lump sum. The tax return is now mostly online, and not too bad if your affairs are otherwise simple. The hardest part will be keeping a good record of your other earnings. Remember that you have to keep these records for seven years in case HMRC ever want to audit them, and it's a good idea to have a separate account for the income, or some other way of easily identifying it. 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, as a director normally you can't. As a director of a Limited company, all those payments should be accounted for as directors' remuneration and have been subject to PAYE and NIC, even if you are self-employed. Currently there is no legislation which prevents a director from receiving self-employment income from a company in which he is a director, however the default position of HMRC's is that all the payments derived from the directorship are subject to PAYE. In other words, it's possible only invoice from an unconnected business or in a consultancy role that's not directly related to the trade of business. But it really depends on the circumstances and the contracts in place. Sources: Monsoon at AAT forum, David Griffiths at UKBF, Paula Sparrow and Abutalib at AW  More sources: If a person does other work that’s not related to being a director, they may have an employment contract and get employment rights. Source: Employment status as director at Gov.uk In principle, it is possible for an employee or office holder to tender for work with their employer outside their normal duties, in circumstances where that individual will not be providing service as an employee or office holder but as a self-employed contractor. Where there is any doubt about whether service is provided constitutes employment or self-employment, see the Employment Status Manual (ESM). Source: Section 62 ITEPA 2003 at HMRC The Government self-assessment website states you can ask HMRC to reduce your payments on account if your business profits or other income goes down, and you know your tax bill is going to be lower than last year. There are two ways to do this: As a sole trader you would fill out an Individual Tax Return and complete the Business and Professional Items Section P1 to P19, then enter the amounts from that section into Item 15 in the Supplementary Section of the Tax Return. Any business income as a sole trader will be included into your taxable income for the year together with other sources of income you may have earned in the same income year. Whether you get a tax refund will depend on the amount of taxable income you make, the amount of tax you have already paid in instalments throughout the year, and any tax deductions and tax offsets you can claim. "The P11D is a record of the total benefits you've received in a tax year that haven't been taxed in another way, a bit like the P60 is a record of the total pay and tax you've paid in a tax year. Note that travel for business purposes shouldn't be taxable, and if that's what's being reported on the P11D you may need to make a claim for tax relief to HMRC to avoid having to pay the tax. I'm not sure whether it's normal for such expenses to be reported there. HMRC will normally collect that tax by adjusting your tax code after the P11D is issued, so that more tax is taken off your future income. So you don't need to do anything, as it'll be handled automatically. As to how you know it's accurate, if you have any doubts you'd need to contact your former employer and ask them to confirm the details. In general you ought to know what benefits you actually received so should at least be able to figure out if the number is plausible. If your ""travel"" was a flight to the USA, then probably it was. If it was a bus ticket, less so :-) If you fill in a tax return, you'll also have to report the amount there which will increase the tax you owe/reduce your refund. You won't be charged twice even if your tax code also changes, as the tax return accounts for the total amount of tax you've already paid. For travel benefits, the exact treatment in relation to tax/P11Ds is summarised here."