UNION Joins

I am having problems producing the following report.

The function of this report is to list people who have not paid their account in 30,60, and 90 days.

In the BillingRun table, there is a dateprocessed field.
this is the date to check against the paydate field in the payment table.
i.e. if their account is in debit, check to see when a payment was last made.

Using the following columns:
Sitename , Child Name, Debt Age, Amount Outstanding,

Debt Age would be 30 days, 60 days or 90 days+
I am using a datediff(day,billingrun.dateprocessed,payment.paydate) to get the age of the debt.

Rpt_ageDebtorsForSite (@cmb1 as varchar(100)) with encryption as
Begin
Would suggest a union. i.e. create a select statement for the 30 days to 59 days UNION select statement for 60 to 89 days UNION select statement for 90 + days

i.e. SELECT S.SITENAME,C.FORENAME+€™ €˜+C.SURNAME,€™30 DAYS€™,TOTAL
WHERE DEBT BETWEEN 30 AND 59 DAYS OLD
UNION
SELECT S.SITENAME,C.FORENAME+€™ €˜+C.SURNAME,€™30 DAYS€™,TOTAL
WHERE DEBT BETWEEN 60 AND 89 DAYS OLD
UNION
SELECT S.SITENAME,C.FORENAME+€™ €˜+C.SURNAME,€™30 DAYS€™,TOTAL
WHERE DEBT 90 DAYS OR GREATER OLD
End

This is what i have so far,

CREATE procedure rpt_ageDebtorsForSite
(@cmb1 as varchar(100)) WITH ENCRYPTION
AS
BEGIN

SELECT DISTINCT

Site.siteName,
Child.surname + ' ' + Child.forename AS Child_Name,
datediff(day,billingrun.dateprocessed,payment.paydate) AS DebtAge
--

FROM Site
INNER JOIN
BillingRun
ON Site.siteID = BillingRun.siteID
INNER JOIN
payment
ON Site.siteID = payment.siteID
INNER JOIN
Child
ON Site.siteID = Child.siteID


select
amount
from
payment AS Amount_Outstanding


--WHERE
--site.sitename=@cmb1
END


The output should look like

Sitename: childname: debtage: amount_outstanding
HappySite mary 10 100