no need for group by clause to see the whole years benefits paid.
I don’t know that I precisely understand your question, but if you are wanting to group all months into a single year and display the amount of benefits paid for the year, this is a possible solution based on your example.
select substr(year_mnth,1,4) Year, sum(benefits_paid) Benefits
group by substr(year_mnth,1,4);
This would output:
You can format this output in a variety of ways. I hope this helps.