You don't need the RTRIM at all. Here's an example.

WITH Customer(Source) AS(

SELECT 'CREDITNEW' UNION ALL

SELECT 'CREDITNEW ' UNION ALL --Spaces added

SELECT 'CREDITNEW' UNION ALL --Tab added

SELECT 'CREDITOLD' UNION ALL

SELECT 'TOC')

SELECT * ,

CASE

WHEN RTRIM(Customer.Source) IN ('CREDITNEW','CREDITOLD','TOC') THEN 'CREDIT'

WHEN RTRIM(Customer.Source) IN ('DEBIT') THEN 'UC DEBIT'

WHEN RTRIM(Customer.Source) IN ('DEBITOLD','DEBITNEW','TLC') THEN 'DEBIT' -- Defined orginally with space, Crystal uses the space version for logo

ELSE 'UNDEFINED' -- Default logo

END AS CompanyName,

CASE

WHEN Customer.Source IN ('CREDITNEW','CREDITOLD','TOC') THEN 'CREDIT'

WHEN Customer.Source IN ('DEBIT') THEN 'UC DEBIT'

WHEN Customer.Source IN ('DEBITOLD','DEBITNEW','TLC') THEN 'DEBIT' -- Defined orginally with space, Crystal uses the space version for logo

ELSE 'UNDEFINED' -- Default logo

END AS CompanyName

FROM Customer