Nachbesteuerung - experiences or advice?

[Filosofen]

While filling our tax declaration for 2020, I figured out that in our 2019 declaration I had missed to declare an investment account (it had been opened in 2019). Thus missing 200-300 chf worth of income.

Anyone has experiences of declaring income/assets afterwards, which were initially missed/forgotten? I keep reading about that you are allowed to do this once in a lifetime, without any consequences.
What happens if I in X years again realise that I’ve missed something minor? What are the penalties after this first time?

There is a Nachbesteuerung option in the tax software, so I assume I simply upload the relevant documents and add a short explanation?

[MUFC_OK]

@Filosofen

Thus missing 200-300 chf worth of income

you probably paid withholding tax on this? For that little amount I wouldn‘t bother reporting it.

[HammerOnFire]

@Filosofen

Anyone has experiences of declaring income/assets afterwards, which were initially missed/forgotten? I keep reading about that you are allowed to do this once in a lifetime, without any consequences.
What happens if I in X years again realise that I’ve missed something minor? What are the penalties after this first time?

Do you have a final assessment (definitive Veranlagung) for 2019? If not, you can just inform the tax office and they add the figures in the final assessment 2019. = easiest way

Otherwise you have to decide if you follow strictly the law and go in to Nachbesteuerung or you just declare it in 2020. Personally, I would not report this low figure.