The electrons are transferred when the reaction is redox reaction. It means that there must be reduction and oxidation.
The given equation is
[tex]H_{2}CO_{3} (aq)+2NH_{3} (aq)=2NH_{4}^{+}(aq)+CO_{3}^{-2}(aq)[/tex]
The oxidation number of each element remains the same before and after the reaction.
H = +1
C: +4
O: -2
N: -3
Thus this is simple acid base reaction and not redox
There is transfer of proton from bicarbonate to ammonia
this is not a redox reaction