Selling online - used and new items

Hello, Hope someone can help me clarify this for me as I couldn’t find a definitive answer online or on the forum. I began decluttering and selling used clothing and other used household items. I understand this would not need to be declared. However, I also started to sell items with profit making in mind. I understand this will need to be declared, no problem. My issue is that I have used the same online account, so there is a mix of used items (not declarable) and profit seeking items (declarable). I understand I probably should have separate accounts for each activity where the market place allows. I don’t have receipts for many of the used items. Is it possible to estimate the cost of them ? Or, is it acceptable to disregard the used items in calculating my gross profit and provide details of this in the ‘additional notes’ section ? Or will I just have to take the hit and be taxed on them ? Thank you

Hi Rokee99,
If you are disposing of personal possessions, then this falls under the rules for Capital Gains Tax.
Have a look at the guidance here:
Capital Gains Tax on personal possessions
It is only when capital gains disposal exceed your annual exempt allowance of £3000, that you would be required to declare the gains.
If you are buying stock to sell, then you are trading and if the gross turnover exceeds £1000 in a tax year, you need to register as self employed and complete a tax return.
What a sole trader is
Thank you.