SQL Server: Query Efficiency Having vs Subquery
If your table's clustered index has pd_dt as the first column, this may be the most optimal query. You could simplify it by breaking it into two parts, like so:

DECLARE @dt date;
SELECT @dt=DATEADD(month, -12, CAST(MAX(pd_dt) AS date)) FROM DW_STAGE.ETL.Claims;

SELECT * FROM DW_STAGE.ETL.Claims WHERE pd_dt&gt;@dt;


Things you could do to improve performance:


Reduce the number of columns from * to those specific columns that you need.
Create a covering, non-clustered index for these columns, where the first column of the index is pd_dt or pd_dt DESC.