What are the countries that require remitter IBAN?

Update July 2022: In Spain, the IBAN requirement is no longer required for the majority of banks, including the biggest ones in terms of coverage (Sabadell, Santander, BBVA, ING Spain and Bankinter). It is now worth noting that:

• Caixabank only supports this option for domestic transfers;
• Imaginbank, part of CaixaBank, are working on a fix and should remove this requirement in the coming months.