  We derive exact sum-rules that relate the tunneling density of states (TDOS)
of spinful electrons in the fractional quantum Hall (FQH) regime to the
spin-dependent many body ground state correlation energy. Because the tunneling
process is spin-conserving, the 2D (two-dimensional) to 2D tunneling current
$I$ at a given bias voltage $V$ in a spin-polarized system is a sum of majority
and minority spin contributions. The sum rules can be used to define
spin-dependent gaps that we associate with peaks in 2D to 2D tunneling $I-V$
curves. We discuss different scenarios of tunneling between layers at different
fillings in relation to our sum rules. We comment on what recent tunneling
experiments say about spin-dependent correlations in light of our sum rules,
and propose additional measurements that could provide more specific
experimental estimates of spin-dependent correlation energies.
