Upvote:1
When renting in the US, the largest companies make it optional, including:
To answer your original question, there isn't an source of these types of letters for when you do need them outside of your card issuer. A benefits guide might work in a pinch, but Mexico in particular may a letter from your card issuer with specific requirements, and CDW is not optional there. Other countries require that the CDW is included in the rate, but it depends on the specific situation.