1) Learn some accounting first. I see a ton of truly weird debates about economics and taxes that are based completely false ideas of basic accounting concepts.
2) If you use DEGIRO as a broker, make sure you understand the tax implications of their cash handling. They keep customer "cash" in a money market fund, not in a bank account. This is especially relevant if you hold foreign currency in your account. It's also relevant if the amount of disposals in each tax year has consequences for your tax return (such as the £45000 threshold for submitting a CGT return in the UK).
So what DEGIRO does is that they buy shares in a money market fund (MMF) with any cash balance that's left in your account at the end of each day. This is done on your behalf like an standing order.
For instance, if you transfer money into your DEGIRO account or you sell stocks and don't use (or transfer) that money on the same day, DEGIRO will move your money into the MMF. So you are effectively buying MMF shares.
When you use your money at a later date to buy securities or because you want to transfer money out of the DEGIRO account, they will automatically sell MMF shares on your behalf to cover the cost.
In some tax jurisdictions this disposal of MMF shares may be subject to capital gains tax (or other taxes). The exact tax treatment depends on the tax status of the MMF in the country where you pay taxes (usually where you live). You may also have to pay taxes on any interest you receive from your MMF shares.
Now, if the base currency of your DEGIRO account is the same as the currency in which you owe taxes and you're using Auto-FX (that is you're not holding other currencies in your account), this whole structure is unlikely to affect the amount of tax you owe. The price of the MMF hardly changes at all, so there will not be any taxable gains or losses in the fund currency.
But if you pay taxes in a currency other than the base currency of your DEGIRO account or you don't use Auto-FX, then any change in exchange rates may cause taxable gains or losses on disposal. You may also have to report the number of disposals, the total proceeds from disposals and/or each individual disposal in your tax return, even if no gains or losses have resulted from those disposals.
That's why it's important to know what the tax treatment of those money market funds is in your jurisdiction and if you have to include the MMF disposals in your tax return or not. Are the MMFs registered in your country at all? If not, you may have to pay higher taxes on any gains. Are they transparent for income tax? There are many questions.
It's easy to think of DEGIRO's strange structure as an internal affair for them. But that is not necessarily the case depending on the tax laws of your country and the tax status of these particular money market funds in your country.
DEGIRO is a Dutch company. They report all disposal proceeds as well as any interest income to the Dutch authorities who will then pass that information on to the tax authorities of your country of residence under CRS (Common Reporting Standard) rules.
Obviously, the information the tax authorities receive from DEGIRO should be consistent with what you report in your tax return. It's all the more important to understand the tax implications of DEGIRO's cash funds as mistakes you make in an offshore brokerage account may incur far higher penalties than the same happening in a domestic account.
I asked DEGIRO about the tax treatment of their money market funds. Their reply: "We don't give tax advice".
1) Learn some accounting first. I see a ton of truly weird debates about economics and taxes that are based completely false ideas of basic accounting concepts.
2) If you use DEGIRO as a broker, make sure you understand the tax implications of their cash handling. They keep customer "cash" in a money market fund, not in a bank account. This is especially relevant if you hold foreign currency in your account. It's also relevant if the amount of disposals in each tax year has consequences for your tax return (such as the £45000 threshold for submitting a CGT return in the UK).