Thanks. Resolving the expensive iTVF results in this:
DATEADD(dd, -1, @year + '-' + MONTH(b.shpdate) + '-01')
Can you post the code for populating the variable @year?
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden