How to display tax inclusive pricing on the product page

[Hannah20]

Hello!

I am based in the UK but sell predominantly overseas so show VAT-exclusive pricing. However, to sell in the UK, I need to charge VAT. I need this to be shown on the product page as I don't want the customer to be surprised at checkout with an additional 20 percent. 

Apparently, the Shopify theme that I use does not allow this and requires some coding. Does anybody know how to do this?

Thank you in advance for any help!