When Degiro receives your money, Degiro will automatically invest your money to Money Market Funds (MMF). This is because it is illegal for Dutch brokers to hold money. When you want to buy shares, Degiro converts the MMF to money and then buys the share.
Do these events (MMF buy/sale) create any tax liabilities for me? Do I need to declare them to the Swiss tax authorities?
You should just declare gain/loss of these funds.
You have all on the annual report provided by Degiro.
That would be capital gains taxes, so no, not in Switzerland.
Do I need to declare these? I made a profit of 0.31 CHF in total (lol).
You need to declare your cash holdings in DeGiro. But any earnings of less than 0.50 CHF gets rounded down to 0 anyway (experience from ZH and BE). You’d just declare 0.
Cool thanks for the tax filling lesson.