Where can I find the expiry date of the haven car seat?

The haven has an 8 year expiry from the production date (for models 2018+).

The manufacture date of the seat is the most recent date which has been hole punched (there may be a few dates stamped).
This example shows October 2017

For older haven booster seats you can find the production date on a sticker similar to the picture below on the back of the outer shell:

haven booster car seat expiry date sticker example