my %details_for = ();
for (... [your loop beginning here] ...){
   my $trans_details = $details_for{$comp_ident};
   unless ($trans_details){
      $trans_details = [];   # first time for this company.
                             # create its array of details.
      $details_for{$comp_ident} = $trans_details;
   }

   # Add to array of trans details for this company
   push @$trans_details,
      { company_ident => $comp_ident,
        company       => $company,
        ... etc.,
        debits        => $debits,
        credits       => $credits
      };
}

# Ok, now you've accumulated the data
print STDERR Dumper(\%details_for);   # just for debugging.

# Print the results:
foreach my $comp_ident (keys %details_for){
   my @trans_details = @{$details_for{$comp_ident}};
   my $comp = $trans_details[0]->{'company'};
   my $sumcredits += $_->{'credits'} for (@trans_details);

   # Show the total credits
   print $comp, "\t", $sumcredits, "\n";
   foreach my $trans(@trans_details){
      print " " x 3;   # indent a little
      print "effective: ", $trans->{'effective_date'};
      print ". created: ", $trans->{'date_created'};
      # etc.
      print "\n";
   }
}