Gross income is actual income less expenses. This is the profit, remember your talking "company" accounts here.
The exemption is potentially reducing taxable income which is taxable at the relative rate.
So you have a £1k allowance you
can use.
Eg you sell £3k worth of goods, you have costs of £2.5k you made £500 profit.
OR, you can substitute the £2.5k with £1k allowance.
Its designed that for small people with low income of less that £1k HMRC just exempt it.
Clearly if you have sales of £3k your not doing a very small side hustle, so you need to declare.
Remember
If you use the trading or property income allowances you must keep a record of your income.
Examples of the records you may need to keep are:
- copies of your invoices, paper or electronic
- a spreadsheet of your income receipts
- emails confirming income received
- statements from the company who paid you which show the amount you received
- bank statements
- bank deposit pay-in records
- a diary or appointments book showing your income from each customer
HMRC can charge you a penalty if the records you keep are not accurate, complete and readable or if you do not retain them for the required period of time.
Summary, don't sell more than £1k of stuff thats not simply your old stuff. If you do you are likely to be liable for tax on the profit.
The profit being the difference between what you sold and the costs, or what you sold and using £1k as the costs, which ever gives you the lower number.
If your selling more than £1k of stuff thats clearly not just your old stuff you need records. Your clearly acting as a self employed trader.