T-SQL (SS2K8) :: Join Clause With BETWEEN Statement

I need to write a SQL script where a join condition is using date columns (effective_date, ineffective_date). The effective date columns can be slightly different (e.g. differ by a day) for some rows of data. I need the join condition to accommodate these date differences and return these rows of data as well.

I have a table which uses multiple joins to create another table but it turns out that the effective_date which is used in the join to match row together does not work all the time since some of the dates for the effective date column are out of sync meaning records that show data as missing even when the other table contains the data. I tried the SQL script below using the BETWEEN clause but it returning 6 rows instead of 3–

select t2.[entity_id]
,t2.[effective_date]
,[company_name]
,[last_accounts_date]
,[s_code]
,[s_code_description]

[Code] .....