If I understand your question correctly, you need cumulative monthly results on the same line as comma-separated delimiters.
create table a (dateval date, acc int,accname varchar(100), debit decimal(10,2)) insert into a values ('20150630', 111110, 'Building Gross Value', 633604.230), ('20150731', 111110, 'Building Gross Value', 2760.000000), ('20150730', 111110, 'Building Gross Value', 1400.000000), ('20150808', 111110, 'BUIIdlngGrossValue', 1890.00), ('20150811', 111110, 'BUIIdlnanossValue', 180.00), ('20150811', 111110, 'Building Gross Value', 375.000000), ('20150819', 111110, 'Building Gross Value', 2622.200000), ('20150821', 111110, 'Building Gross Value', 360.000000), ('20150822', 111110, 'Building Gross Value', 21.600000), ('20150824', 111110, 'Building Gross Value', 100.000000), ('20150825', 111110, 'Building Gross Value', 770.000000), ('20150829', 111110, 'Building Gross Value', 100.000000), ('20150831', 111110, 'Building Gross Value', 340.000000), ('20150831', 111110, 'Building Gross Value', 790.000000), ('20150924', 111110, 'Building Gross Value' ,918.750000), ('20150928', 111110, 'Building Gross Value', 2830.000000), ('20151005', 111110, 'Building Gross Value', 1411.000000), ('20151023', 111110, 'Building Gross Value', 625.000000)
Now the query below will give you the results on the same line as commas.
with cte as ( select * from ( select a.dateval,b.acc,b.accname,sum(b.debit) as debit,row_number() over (partition by year(a.dateval),month(a.dateval) order by a.dateval desc) as rn from (select distinct dateval from a) as a inner join a as b on a.dateval >= b.dateval group by a.dateval,b.acc,b.accname ) as a where rn = 1 ) select acc,accname,stuff((select ',' + cast(debit as varchar(1000)) from cte as b where a.acc = b.acc for xml path ('')),1,1,'') from cte as a group by acc,accname