Try
SELECT
p.posid
,v.locgrpcde
,p.paydte
,p.tendercde
,(p.localamt - p.changeamt - p.nochgamt) AS net_amount
FROM
psbillp p
INNER JOIN msPos pv ON p.posid = pv.posid
INNER JOIN msLocation v ON pv.loccde = v.loccde
WHERE
v.locgrpcde = 'GNG10 GROUP'
AND paydte = '2014-04-01 00:00:00.000'
AND tendercde = 'CASH'
GROUP BY
p.posid
,v.locgrpcde
,p.paydte
,p.tendercde;
instead.