In the UK, You must declare all income that is not already taxed at source. Be aware that HMRC are very hot on catching freelancers or traders those are earning money and not declaring it to HMRC. As a freelancer, if you are paid via a payslip (PAYE) and tax is being taken “at source”, you might not need to do anything. It is different, however, if you’re a freelancer, as freelancers are usually paid gross income and therefore it is your responsibility to make sure you do your own tax return, calculate the correct tax, and pay HMRC by the deadline. Now, seeing as this whole exercise is somewhat cumbersome, you like hundreds of other taxpayers can probably use the help of an accountant.In order to work out the amount of tax you need to pay there is a raft of rules, reliefs, and exemptions, which you might misinterpret, miss out on, or miscalculate, but which an accountant can work out for you, and help reduce the amount of tax you will have to pay as well.Remember, anyone who thinks they can get away with not paying tax or not filling out a self-assessment tax return (SATR) for income not already tax at source is seriously misguided. That you can get away without paying tax or “disguise” income is a myth. To this end, HMRC’s ability to snoop into your online transactions, bank accounts, and all other personal records are boundless.If you start working freelance, most likely you’re classed as a sole trader. This means you’re self-employed and you must inform HMRC at the earliest opportunity that you are a freelance or self-employed and register for self-assessment, in order to declare all your income that’s not already taxed at source. You do this on a self-assessment tax return (SATR). This is the same, even if you have a full time job where you are taxed at source as well as doing freelance work.You are freelance, self-employed or a sole-trader if you:Work for yourselfHave several customers at the same timeAre able to decide how, where, and when you do your workHire other people at your own expense to help you or to do the work for youProvide the main items of equipment to do your workAre responsible for finishing any unsatisfactory work in your own timeCharge an agreed fixed price for your workSell goods or services to make a profit (including online on via an app).From 6 April 2017, the money you can earn before paying income tax (called the Personal Allowance) is £11,500 (up £500 from 2016). But you must still report all your income and pay national insurance and income tax on self-employed income, and you should report all income above the stipulated allowances.As a freelancer, you and you alone are responsible for ensuring the correct amount of tax and national insurance is paid by the deadline (31 January in each tax year). And you must make sure you have the money to pay your tax and NI when it’s due, or you will be hit by penalties and fines that grow the longer you leave paying them.These are your responsibilitiesYou’ll need to:Keep records of your business’s sales and expenses (and hold on to them for at least six years)Send a Self Assessment tax return every yearPay Income Tax on your profits and Class 2 and Class 4 National InsuranceYou can use the HMRC calculator to find out how much you are likely to have to pay in tax and national insurance.It is not a legal requirement to run a separate business bank account, but it is advisable to have a bank account that is separate from your personal bank account.What MUST YOU DO as a freelancer, self-employed or sole-trader?You must pay tax on business profits (see the thresholds here);You must pay class 2 National Insurance contributions (NICs) at £2.85 per week (unless you earn less than £6,025 per year);And you must pay class 4 NICs on profits over £8,164 at 9% up to £45,00, and then 2% thereafter.The amount of income tax and class 4 national insurance contributions you pay will depend on the information you provided in your SATR.Do you need an accountant?Some freelancers use an accountant to do their accounts and submit their self-assessment tax return to HMRC. These freelancers tend to benefit from an accountant knowing exactly which expenses are allowable and can be offset against tax, and be 100% certain that they are getting all the allowances and benefits they are due.In addition, an accountant will avoid costly mistakes and errors. So while it may seem cheaper to do your own accounts and file your own SATR, it’s likely an accountant will save you time and save you money in taxes, which will add up to a lot more than what you pay in accountancy fees. Also remember that accountancy fees are an allowable expense!