The standard rate of VAT is currently 20%. This rate should be used unless the goods or services are classed as reduced (5% VAT) or zero-rated.
Some products are also exempt from VAT, things like postage stamps and insurance.
Read HMRC’s guide to VAT rates on different goods and services for the full list (link to HMRC page: https://www.gov.uk/guidance/rates-of-vat-on-different-goods-and-services)