What system is used to pay your own tax if you are self-employed?

When you work for a company, your employer deducts income tax and National Insurance contributions directly from your wages through a system called PAYE, or Pay As You Earn. But if you're self-employed, you're essentially running your own business, and that means you're responsible for calculating and paying your own income tax and National Insurance. This is done through a system called Self-Assessment. Think of it as you, the individual, assessing your own income and tax liability. Every year, you'll need to fill out a Self-Assessment tax return, declaring your income and expenses to HMRC, the UK's tax authority. They then calculate how much tax you owe. It's a key part of being self-employed in the UK. Self-checkout is a system used in shops, Trade Unions represent workers, and National Insurance contributions are part of the tax system, but not the system for self-employed people to pay their income tax.