All information is correct at the time of writing. We always recommend that you confirm with your own research.
You must register your business for VAT with HM Revenue and Customs (HMRC) if its VAT taxable turnover is more than £85,000 (2022/23) annually.
As a sole trader or self-employed yoga teacher, it's unlikely that you will meet this threshold, in which case you will not need to charge VAT on your classes.
Larger yoga businesses such as studios and training providers are a different matter. If you believe that your turnover is close to, or meets, this threshold you must do your research and seek advice in plenty of time.
We would recommend the following resources:
VAT: Basics yogatax.co.uk
VAT Registration gov.uk