IMPORTANT § 6AB: if you are not on a monthly payroll you ARE NOT an employee. If you send invoices working for a company you are self-employed.
IMPORTANT § 6B: Invoicing foreign clients (with a CZ trade license) IS NOT foreign Employment (do not tick the § 6B box but § 7 instead).
IMPORTANT § 6AB+ 7: If you are employee and have a CZ trade license - even if you made no money with your TL, overviews for social security and health need to be filed, so also in the case of no revenue with your TL, tick the § 7 box.
IMPORTANT § 7: Income with a Czech Trade License or other Czech free profession - invoicing clients in CZ, in EU and outside EU.
Also any AirBnB revenue fits here - since you are required to have a Czech Trade License *and VAT registration* to operate AirBnb. In case you do not have a Czech TL or VAT registration this needs to be addressed asap(!).
IMPORTANT § 8: regular small interests on personal bank accounts are usually deducted at source and DO NOT need to be entered in §8.
IMPORTANT § 9: rental income from abroad IS NOT taxed in Czech Republic
IMPORTANT 10A: Invoicing a foreign client with your Czech Trade License *is not* foreign self-employment. Foreign self-employment means: being registered in that country as self-employed. If you are only registred in CZ, then select §7.
LLC / Foreign Business Profits may fit in §7 or §10 - depending whether you have a CZ trade license and whether the foreign business is (considered) sole proprietorship (file in §7 with active CZ TL) or an independent legal entity with a dividend payout (usually file in §10A).
IMPORTANT § 10B: vested shares should be declared in the year they were vested, as they are considered employee benefits.
Selling of shares, capital gains / payouts from investment portfolios and profit on property may be tax-exempt (the so-called 3-year rule).
Capital gains from trades under 100.000 CZK, but not exempt by the 3-year rule, still do not need to be declared in the Tax Return.