something is not very clear to me
let's say i have a foreign LLC company, and i make some profit there, and i never pay a single dividend, do i still need to declare it in my personal tax filings?
or i can just defer taxation indefintely?
(i'm a EU citizen, not US)
It depends on local law where you are based and how LLCs (specifically LLCs from wherever yours is incorporated) are treated there.
If you're US resident, the earnings of an LLC are generally always taxable personal income. Sometimes that principle is applied in other jurisdictions, sometimes it's not.