The Rent a Room Scheme lets you earn up to a threshold of £7,500 per year tax-free from letting out furnished accommodation in your home. This is halved if you share the income with your partner or someone else.
You can let out as much of your home as you want.
The tax exemption is automatic if you earn less than £7,500. This means you do not need to do anything.
If you earn more than this, you must complete a tax return. You can then opt into the scheme and claim your tax-free allowance. You do this on your tax return.
You can choose not to opt into the scheme and instead record your income and expenses on the property pages of your tax return.
You may need to calculate the tax effects of both options if your gross rental income from letting a room or rooms at home is more than £7,500.