It depends on whether you are a "VAT registered trader/business"
If you are registered then you charge your customers VAT on their purchases, but you offset against this the VAT you paid when you bought it, and then pay the difference to HMRC.
If you are not VAT registered then you can't charge your customers VAT on their purchases, and you therefore have to absorb any VAT you paid when you bought the item into your costs/overheads because there is nothing to offset it against