Another opinion.

declare @CurrentDate datetime = dateadd(month,1,getdate()); -- Say current date is a month from now. In the declares below you could use GETDATE() instead.

declare @StartDate datetime = dateadd(month,datediff(month,0,@CurrentDate) - 1, 0),

@EndDate datetime = dateadd(month,datediff(month,0,@CurrentDate), 0);

select @CurrentDate, @StartDate, @EndDate;

-- Your query would look something like this:

select

-- your columns --

from

dbo.YourTable

where

YourDateColumn >= @StartDate and

YourDateColumn < @EndDate;