You should already know the amount when you file your taxes, at the end it tells you your tax due.
Quick update. All I had to do was attach a simple letter where I described how some of the stocks declared in my 2024 tax returns grew in the course of 2025. And how the resulting growth is below our annual spend (which is very credible). And I just got my tax decision and reimbursement of overpaid tax on my bank account. So I was worried for nothing.
However, it is still frustrating they grow suspicious of people and ask for justifications, when they have all the data to begin with. Would have taken them a minute if they bothered. But well, at least all worked out in the end, and from my experience once they clear a certain issue with a person, they don’t come back to it again (in my case, one year they had questions about childcare costs, another year it was about 2nd pillar repurchasing, etc, but they don’t come back to the same topic, every time it’s a different type of question).
Thanks again and all the best with your 2025 tax returns if not finalised yet!
It’s good to hear that everything worked out. Just out of curiosity: Did the tax office from the gemeinde or the tax office from the canton contacted you?
Canton (Vaud)
You also could have sold all your stocks in the beginning of January, got a 6 digits gift, didn’t spend it all and reinvested in the same securities in December. How do they suppose to know if they don’t ask?
I’ll let you know next year if I will be scrutinized likewise, my YTD growth is far beyond my annual salary.
But they do ask already. In the tax returns you are supposed to indicate all transations (sales and purchases).