Hey all. I'm a bit lost here, so I'll try to give as much context as I can.

As a reference, I'm in Spain and we are talking of 2021 taxes.

• I worked for Company A all of 2020 until the end of january, 2021. My salary was X€ per year plus a "bonus" amount that most years was given.

• After I left Company A, I got the "finiquio" (last payroll with all the money owed to me and whatnot), but not this "bonus." I asked for it, and they paid it to me. So far, so good.

The problems I have are two:

1) I've realized that even in january "finiquito" appears an amount for "Seguridad social" (Which I assume is the amount to the IRPF), the Certificado de retenciones they've sent me appears as if there were no retentions (0). They are using a different language from my current company,

2) The biggest issue, the bonus appears also as having no retention, but it also has a (tiny) amount of money as "Seguridad social", but I'm not really sure on how this "bonus" works regarding taxes (And I've guessed is the main culprit that I'm getting my ass handed to me with the taxes for this year).

I'm going to ask the guys of HR about this, but taking into account that they can just tell me to fuck off, I would like to get some feedback here, specially on how these "bonuses" work and how they are taxed.