MS SQL: Count payments for a given periode

SELECT cus.CustomerStartDate, COUNT(cus.CustomerNo)AS NumberOfWeb
FROM Company.dbo.Customer cus
WHERE cus.SourceCode = 'Web'
AND cus.customerStartDate > '2012-01-01'

AND EXISTS (
	SELECT 'x'
	FROM Company.dbo.Payment py
	WHERE cus.CustomerNo = py.CustomerNo
	AND py.PaymentAmount > 0
	AND py.PaymentDate BETWEEN '2013-01-01' AND '2013-02-01'
	having count(*) = 1) 

SELECT cus.CustomerStartDate
     , COUNT(*) AS NumberOfWeb
  FROM Company.dbo.Customer cus
INNER
  JOIN ( SELECT CustomerNo
              , MIN(PaymentDate) AS first_payment
           FROM Company.dbo.Payment
          WHERE PaymentAmount > 0
         GROUP
             BY CustomerNo ) AS pay
    on pay.CustomerNo = cus.CustomerNo
 WHERE cus.SourceCode = 'Web'
   AND cus.customerStartDate >= '2012-01-01'
   AND pay.first_payment >= '2013-01-01' 
   AND pay.first_payment  < '2013-02-01'