Hi,
If you have a gross turnover of less than £85000, then the VAT on the cost of the item you purchased is part of the expense of acquiring the product and is included as part of the acquisition cost.
When you sell the product on, including VAT, the disposal value including VAT is declared as part of your gross turnover. The VAT included as part of the selling price, is claimed as an allowable busines expense. You can see guidance here:
HS222 How to calculate your taxable profits (2023)
Thank you.