Query to get Count of Payable Invoices by Year and Status (Paid, Unpaid or Cancelled)

We were purging payable invoices and i wanted to know how many invoices are still not paid in a given year. So i used this simple query.
select to_char(last_update_date,'YYYY') Year , sum(decode(payment_Status_flag,'Y',1, 0)) "Paid Invoices" , sum(decode(payment_Status_flag,'N', decode(cancelled_date,NULL,1, 0),0)) "Unpaid Invoices" , sum(decode(payment_Status_flag,'N', decode(cancelled_date,NULL,0, 1),0)) "Cancelled Invoices" from ap_invoices_all where last_update_date between to_date('01-jan-2015','dd-mon-yyyy') and to_date('01-jan-2020','dd-mon-yyyy') group by to_char(last_update_date,'YYYY') order by 1;