Deregistration / termination of temporary visa

Hello everyone,

I am a US expat on a temporary working visa, and will be leaving my job here and the country in March.

I was wondering what the departure procedures are. Do I need to "deregister" (terminate by temporary visa) in a formal way (officially announce my permanent departure to immigration)? If so, what is the bureau that handles this, and is anyone familiar with the process?

You will of course need to present your DNI to migraciones as you depart. You don't have to tell them anything and you can keep your DNI as a souvenir.
right. and this won't affect my taxpayer status in any way, right? i mean, that's determined by my work contract duration, correct? excuse my ignorance, i am young :)