-- This looks correct:
SELECT 
	ERP_ID,
	customer_number,
	ANNUAL_CONTRACT_PRICE,
	[Rank]
FROM (
	SELECT 
		ERP_ID,
		customer_number,
		ANNUAL_CONTRACT_PRICE,
		ROW_NUMBER() OVER (PARTITION BY customer_number ORDER BY ANNUAL_CONTRACT_PRICE DESC) AS [Rank]
	FROM EMEA_SERVICEMAX.Servicemax.SERVICE_CONTRACTS_STG  
	WHERE CONTRACT_START_DATE >= GETDATE()-730 
		AND CONTRACT_STATUS_DESCRIPTION NOT IN ('Free','Canceled','Cancelled')
) a
WHERE a.[rank] <=5 
	AND a.CUSTOMER_NUMBER = '110000053'
	
-- Test it:
SELECT TOP 5 * 
FROM EMEA_SERVICEMAX.Servicemax.SERVICE_CONTRACTS_STG
WHERE CONTRACT_START_DATE >= GETDATE()-730
	AND CONTRACT_STATUS_DESCRIPTION NOT IN ('Free','Canceled','Cancelled')
	AND a.CUSTOMER_NUMBER = '110000053'
ORDER BY ANNUAL_CONTRACT_PRICE DESC

-- Suggestions:
-- Use a variable for the cutoff date and remove the time component
SELECT @CutoffDate = DATEADD(day,DATEDIFF(day,0,GETDATE()-730),0)