SQL the column should return 1

 select d.submittedtimestamp, 
 case when isnull(t.acceptedtestdrive,0) =0 then 0 else cast (t.acceptedtestdrive as float)/cast(count(d.dealid) as float ) end as accepetedtestdrivepercentage,
 case when isnull(t.acceptedtestdrive,0) =0 then 0 else 1- (cast (t.acceptedtestdrive as float)/cast(count(d.dealid) as float )) end as accepetedwithouttestdrivepercentage
  from [MMD_Feed].[dbo].[DealView] d
 left join #acceptedtestdrive t on d.submittedtimestamp= t.submittedtimestamp
  where d.dealstatus='sent'
  and d.alternatedeal='no'
  and d.manualdeal='no'
  and d.shopperaccepts>=1
  and cast(d.submittedtimestamp as date)>=@StartDate and cast(d.submittedtimestamp as date)<=@EndDate
  group by d.submittedtimestamp,t.acceptedtestdrive
  order by d.submittedtimestamp desc