What is the formal charge on each atom in the methyl carbocation?

Each hydrogen atom is formally neutral....they gets ONE electron from each covalent bond...the carbon also gets ONE electron from each covalent bond, and has two inner core electrons, formally the `1s^2`...and so carbon has 5 electronic charges...but NECESSARILY 6 positive, nucular charges... And thus the FORMAL charge is `+1`

Just to add that for the purposes of assigning formal charge, we can go back to very old ideas that we learn when are introduced to bonding. In a covalent bond, electrons ARE SHARED between nuclei. An ionic bond is between a formal anion, and a formal cation, and thus involves the prior TRANSFER of electron.

If we take say methane, with FOUR `C-H` covalent bonds, we split this up to give `4xxdotH`, and a carbon atom with 4 valence electrons. The hydrogen ATOMS are neutral, because they have a positive nuclear charge, and also an electronic charge. And hence the hydrogens are neutral.

Likewise, the carbon atom claims 4 electrons from the four `C-H` bonds, and has 2 inner core electrons (i.e. formally the `1s^2` electrons. And so each carbon has 6 electrons, and there are 6 positive nuclear charges. The carbon atom in methane is also thus electronically neutral.