Must I pay VAT (value-added tax)?

If you must pay VAT depends on the billing address.

None EU customers

If you are a customer from outside of the European Union you don't pay VAT. You pay the net price without any addition. It doesn't matter if you are a private or business customer.
If you have a none-EU VAT ID, do not enter it during the payment.
Regarding VAT regulation, the United Kingdom is treated as an EU member until the end of 2020.

EU customers

Customers with a billing address inside the European Union must pay value-added taxes. The tax rate is your local rate.
Charging VAT inside the EU is required by law.
Business customers with a valid EU VAT Tax ID are excluded by the above regulation. The EU VAT Tax ID liberates you from paying VAT on the inter European commerce. That means you pay the net price of the CloudRadar service without additions.
During the payment process enter your VAT ID so no VAT is charged. If you have a business but you don't have a VAT ID yet, ask your tax office. The EU VAT ID is issued to any company free of charge. Normally this takes only a couple of days.
If you are a business customer without VAT ID the VAT must be charged. CloudRadar has no influence on that.
The VAT ID is validated and it must belong to the registered company.
Use your VAT ID during the payment.

German customers

You must pay VAT regardless you are a business or private customer.