i got the help from the forum. now getting clear but i still not able to get the answer of the below.
1) if only have account key (NO accrual key defined) in M/08, may i know what is the posting like?
gross amount $1000
a) net is $1000
b) net is $1020
2) to me, account key also has GL account linked to it, just like accrual key, to me, it is similar to accrual key but from explanation they are different. so i still cannot have a clear understanding of account key.