Correct VAT Rate for a Foreign-Based Online Course?

Hi

I'm considering doing a course online, it is charged in USD. They are US-based. The tax rate applied looks strange to me. I used an online percentage calculator and it says that the tax is coming in at 18.6%.

Tax should be charged at local rates, no? So would the standard rate of 23% apply or 13.5 reduced rate? I thought 13.5? Either way, 18.6 is either too high or too low - if indeed tax is locally-applied and I think it is.

Thanks.