What are known tax issues with international invoicing?
Usually, when you sell goods, you need to add VAT to the item’s total price. This way, customers can pay VAT to the government through you.
The purpose of VAT is to raise revenue for the government through consumer spending. Because your consumers aren’t from the UK, they would not be obligated to pay UK taxes like VAT.
Instead, they must follow their own country’s laws on consumption taxes.
Thus, you do not need to charge UK VAT on any goods you export to foreign countries. There are, however, certain exceptions. 
For instance, VAT will be applicable if you deliver your goods to a UK address, even if your clients themselves are located outside the UK.
The UK government also requires all invoices to reflect your VAT payable in pound sterling. So, if you don’t charge VAT on a product, your invoice needs to indicate that the VAT payable is £0.
This way, the HMRC can use your invoices as evidence of removal, proving that the goods left the country.
Our article ‘What is a valid tax invoice’ also notes that invoices in foreign currency should include the VAT payable in GBP.
In case your VAT payable is not 0, you need to convert your total payable VAT using either the HMRC’s period rates of exchange or the UK market’s selling rate during the time your item was supplied.
Since you’re not charging VAT, clients become responsible for paying their consumption taxes. Even certain countries have provided suppliers with the option to handle consumption taxes on behalf of their customers.
The EU, for example, has the Import One-Stop-Shop (IOSS), which is an electronic portal that allows suppliers to pay EU VAT for their customers.
Suppliers providing goods or services to EU member states can use the IOSS to declare and pay international VAT on behalf of their clients if the sale does not exceed €150.