If you or your company's turnover exceeds the VAT threshold in a rolling year then, unless you or your business is VAT exempt, you will need to be registered for VAT. This means you need to charge VAT on your sales or services but it also means you can claim VAT on your expenses (all subject to VAT qualification).
This is usually done quarterly thought the year.
HMRC has introduced schemes such as Cash Accounting and the Flat Rate Scheme to simplify your returns. We can advise you on which schemes could be best for your business and help you register for them.