SELECT o.order_id AS oid, o.property_address, o.property_address2, o.property_district, o.property_town, o.property_country, o.property_postcode, o.contact_name, (

SELECT SUM( d.price ) AS price
FROM order_to_documents o, documents d
WHERE o.document_id = d.documents_id
AND o.order_id = oid
) AS document_cost, (

SELECT SUM( p.price ) AS price
FROM order_to_package o, packages p
WHERE o.package_id = p.package_id
AND o.order_id = oid
) AS package_cost, (

SELECT SUM( amount ) AS amt
FROM order_payments
WHERE order_id = oid
) AS balance
FROM orders o
WHERE 1
AND (
o.timestamp
BETWEEN '2007-08-04 00:00:00'
AND '2008-08-04 23:59:59'
)
AND (
balance =0
)

MySQL said: Documentation
#1054 - Unknown column 'balance' in 'where clause'