add_line

    my $bool = $invoice->add_line(
        {   name         => "Yard Work",          # (Optional)
            description  => "Mowed the lawn.",    # (Optional)
            unit_cost    => 10,                   # Default is 0
            quantity     => 4,                    # Default is 0
            tax1_name    => "GST",                # (Optional)
            tax2_name    => "PST",                # (Optional)
            tax1_percent => 8,                    # (Optional)
            tax2_percent => 6,                    # (Optional)
        }
    );

Create a new Net::FreshBooks::API::InvoiceLine object and add it to the end of the list of lines.

send_by_email, send_by_snail_mail

  my $result = $self->send_by_email();
  my $result = $self->send_by_snail_mail();

Send the invoice either by email or by snail mail.