Like any other investment portfolio, your portfolio is subject to taxation in your country and your personal situation.
The (variable) IRR will accrue daily. Unlike a deposit where each time interest is accrued, e.g. monthly or annually, tax is normally withheld. In the inbestMe savings portfolio you will accrue interest without deducting any tax.In the case of the fund portfolio, as these are transferable, you can transfer all or part of them to another fund portfolio (for example, in inbestMe, deferring the taxation of your savings/investments as much as possible).
You will only be taxed at the moment of liquidating the portfolio, when you will pay the capital gains tax applicable in your country. In Spain, for example, this is 19% (in most cases).