Once you become a WWOOFer, your account shows your WWOOFer Permit.
It is certification that you are a WWOOFer member of WWOOF Japan for the stated period. 

In the old website up to approx 2020, the WWOOFer Permit had to be printed out and taken with you to hosts’ places. However since 2021 in the new website, hosts to whom you have given permission, can see your WWOOFer Permit via their WWOOF Japan login. Therefore, you do not need to print it out anymore. 

However, you must show your personal ID, such as your passport, to hosts as soon as you arrive at the host's place.
The host will then reconcile your WWOOFer Permit with your personal ID. 

If you are a WWOOFer, please login and read “How to use this site” for more details about the WWOOFer Permit.