the loss claim form on the royal mail website is easy enough to fill out. A screenshot of the sale details is usually enough, and you need the amazon listing ASIN number etc. We've always just claimed the sale value. We only use royal mail 2nd large letter size, there is behind the scenes tracking so they know if its been in their network, you don't need a receipt from the post office etc. Limit off top of my head is £28 but our average value is less than a tenner. Payout from RM usually come in the form of a cheque sent to our shop, guessing usually a week or two to arrive? We sit down once a month and just go through the various claims from amazon. It's settled down now - maybe only 2-4 claims every month (out of 500+ orders). A year ago it was a lot more.

Also claim for delayed delivery if applicable - you tend to receive a book of first class stamps.

MUCH easier dealing with RM for loss and delay compared to Evri - yet to get any sort of compensation or meaningful reply from Evri