I'm about to graduate from a German university. At the beginning of the year, I am working a HiWi (research assistant) job, and the contract ends in March. After I graduate I'm going to take up a full-time job in Germany (e.g. starting in April, or maybe even starting in March, when my HiWi contract is still effective). I think for the full-time job the employer will withhold the tax automatically when they pay you, but apparently the university didn't withhold any tax when they paid my HiWi salaries, since if one only takes the HiWi job, their income will not exceed the personal taxation threshold.
However, with my full-time income, my total annual income will definitely exceed the threshold.
A few related questions ensue:
Does this mean I'll have to "nachzahlen" my taxes for the HiWi part of the income (which according to this post seems to belong to class VI)?
Will it be automatically sorted out when I file my tax returns later in the year, and I don't need to worry about it now?
Does the company need to take my HiWi income into account when they calculate how much tax to withhold (also, I suppose the amount of tax to withhold each month is different depending on whether I start the job in March or in April, since my yearly income would be different)? Or is it not the case since those two income sources could belong to different tax classes.
It all seems a bit confusing.
I wonder if the HiWi income in addition to main job situation is comparable to having, say, income from a side project when you are also working a full-time job at the same time.