Which type of Bonds is present in Ammonia Ion? - QS Study
QS Study

Formation of Ammonia ion (NH4): In ammonia there are three single N-H bonds and a lone pair on nitrogen atom. When it reacts with H+ ion, the lone pair is used to form a coordinate bond between nitrogen atom and hydrogen ion. Thus ammonium ion is formed.

The electrons of nitrogen have been denoted by dot and those of hydrogen atoms by cross. So by definition there are three covalent N-H bonds and one N → H coordinate bond in NH4+ ion.