We prefer you do not use tags issued in previous years - partly due to the fact that the adhesive has a shelf life of about a year.
Datasheets are included in each tagging kit (and available online
as well) as are complete instructions.
Each tag includes an email address and a telephone number you can use to report a tag sighting. If a tagged monarch is spotted alive you should make not of it and release the butterfly to continue its journey.
Hope this helps!