Menopauselbitch
In the UK we have had mandatory fortification laws for decades which apply to most "ordinary" non-wholemeal wheat flours
It used to be "just" Calcium Carbonate, Iron, Niacin, and Thiamin but now includes Folic Acid as well.
This applies to:
Standard white flours - such as supermarket own brands as wrll as named brands such and Homepride (both plain and self-raising)
Also Strong white bread flour
Strong brown flours
other Brown flour (that isn't 100% wholemeal)
Most general-purpose or cake flours.
The folic acid was brought in to help prevent neural tube defects.
Exemptions are in place for:
artisan mills that produce less than 500 metric tonnes of flour and for
less usual grains (eg einkorn, spelt, semolina or rice flours.)
100% Wholemeal doesn't need to have it.
There used to be a workaround by buying imported flours from (say) France or Italy but that loophole was closed some time ago. 2022 I think, from memory.
This is true now even if bought by the sack instead of by the bag.