Accounts receivable (invoices - applied credits)
Just Invoices
Accounts receivable, with deferred revenue (invoices - applied credits, with charges for annual/semi-annual/quarterly/etc. services deferred over applicable time period) (there has got to be a shorter description for this)
Cashflow (payments - refunds)

From <% my @m = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec); foreach my $m ( 1..12 ) { %> <%= $m[$m-1] %> <% } %> <% foreach my $y ( 1999 .. 2010 ) { %> <%= $y %> <% } %> to <% foreach my $m ( 1..12 ) { %> <%= $m[$m-1] %> <% } %> <% foreach my $y ( 1999 .. 2010 ) { %> <%= $y %> <% } %>