Originally Posted by xobile

Technically it is not needed but I would recommend bringing the old passport on trips just in case immigration throws up a fuss. And a printout of the relevant legislation regarding renewal only for the first passport issued after the age of 20. likely from the bureau of immigration and the contracted provider in your country. Also be sure to update the passport number online as that is required for all new passports for under the age of 20 (should be for all ages tbh).