More information on IOSS:

IOSS allows a taxable person to register in a single Member State to declare, and pay, European Union (EU) import VAT. The IOSS can only apply to certain supplies. Where the IOSS is availed of, the import VAT due is not collected by Customs. The import VAT is, instead, remitted through a monthly IOSS return.

The IOSS can be used to declare, and pay, the import VAT due where:

• the goods in question are located outside the EU at the time they are sold
• the goods are dispatched in consignments of an intrinsic value not exceeding €150
• orders over €150 can incur customs charges as this does not qualify for IOSS
• and the goods in question are not subject to excise duties
  

Full information surrounding IOSS - https://www.revenue.ie/en/tax-professionals/tdm/value-added-tax/part10-special-schemes/vat-ecommerce-rules/import-one-stop-shop-ioss.pdf

Rates of EU IOSS VAT charged by The Broken Binding: