Subquery returned more than 1 value error

I am trying to add a column to my results that shows a conditional total but I keep getting the following error:

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

My query is below:

--Outstanding pledge balances

select g.giftid
            ,g.gifteffdat
            ,g.gifttype
            ,g.giftjntamt
            ,(select g.giftamount as BalanceDue from gifts_full where gifttype='p')
            ,g.giftkey
            ,g.giftplgkey
            ,g.giftjntrat
            ,g.giftorigpl
            ,g.gifttpledg
            ,g.giftsolnam
            ,g.giftclass2
            ,g.gifttender
            ,p.paylinkkey
            ,p.payid
            ,p.payduedate
            ,p.paydueamt
            ,p.paybalamt
            ,s.sumJOINTctr
            ,s.sumNOBILLctr
            ,n.namesmashd
            ,n.nameformn
            ,n.nameplural
            ,c.chart_val
            ,d.table_val
from gifts_full g left outer join payments_full p on g.giftkey=p.paylinkkey
          left outer join payments_VIEW_schedule_total_by_fy s on g.giftkey=s.paylinkkey
            left outer join names_VIEW_preferred n on g.giftid=n.nameid
            join chart_of_accounts c on g.giftrest=c.chart_code
            join division d on c.chart_div=d.table_code
            --left outer join (select g1.giftamount as g1.BalanceDue from gifts_full) g1 on g1.giftkey=p.paylinkkey
where g.gifttype in ('p', 'y', 'w') -- only include pledges and payments
            and g.giftjntkey<2 -- exclude joint recipients
            and g.gifttpledg>0

I am trying to show a balance due for any outstanding pledges - if the gift type is 'p' then giftamount as BalanceDue.

As always, any help is GREATLY appreciated!!

Lisa