G'day myhome,

Welcome to the monastery.

Firstly, splitting CSV lines on /,/ is generally not a good idea: that technique falls flat on its face as soon as any data contains a comma. Take a look at: Text::CSV.

To access data in your hashes, you'll want something like $balance{$id}{due_date}. You'll probably want to use the keys function something like this:

for my $id (keys %account) {
    my $name = $account{$id}{name};
    my $cdate = $account{$id}{cdate};
    my $account = $account{$id}{account};
    my $odue = $account{$id}{odue};
}
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For a basic introduction to hashes see perlintro - Perl variable types. More complete details are in perldata. For complex data structures, such as Hashes of Hashes, which is what you're working with here, see perldsc (Perl Data Structures Cookbook).

Finally, please edit your post so that code and data are in <code>...</code> tags, paragraphs are in <p>...</p> tags, bullet lists are in <ul>...</ul> tags, and so on — full details are in Markup in the Monastery.