Add IOSS to letter sized envelopes. Items of value (such as stickers, a greeting card) can and are sent in letter sized envelopes.
Small items of value that are sold by small businesses in the UK (through platforms such as Etsy) and sent to the EU have to be posted as a large letter in order to meet IOSS rules because Royal Mail does not print IOSS on a letter sized envelope.
Printing IOSS on a letter would save EU customers who have paid VAT at the point of ordering from paying VAT once again on receipt of the package This is more expensive than it needs to be for both parties because items such as a greeting card, a small pack of stickers, an iron on patch and more are perfectly ok to fit in a letter sized envelope. In a cost of living crisis it seems unnecessary to force a higher postage cost. Items sent to other parts of the world such as the US can be sent as a letter.