All students applying in the UK for a period of 6 months or more than that will need to pay Immigration Health Surcharge (IHS), which is a part of your visa application. If you’re staying there for less than 6 months then you don’t need to pay for it.
If you’re applying for a visa extend inside the UK, you’ll be required to pay IHS even if your course length is less than 6 months. The fee depends on the length of stay. You’ll be required to pay £470 for every stay that lasts 6–12 months and £235 for an additional period which is less than 6 months.