This is simple Code to get Invoice settlement amount data for customer payment in ax 2012. This data is after posting of data.
If you want get settlement amount before posting than you can refer spectrans table.The table SpecTrans contains all the transactions marked for settlement for payment journal.
  select sum(SettleAmountCur) from custSettlement where  
           custSettlement.TransRecId == custtrans.RecId  
If you want get settlement amount before posting than you can refer spectrans table.The table SpecTrans contains all the transactions marked for settlement for payment journal.
 while select spectrans  
 join custtransopen  
 join custtrans  
 where spectrans.SpecCompany == ledgerjournaltrans.DataAreaId &&  
 spectrans.SpecTableId == ledgerjournaltrans.TableId &&  
 spectrans.SpecRecId == ledgerjournaltrans.RecId &&  
 spectrans.RefCompany == custtranssopen.DataAreaId &&  
 spectrans.RefTableId == custtranssopen.TableId &&  
 spectrans.RefRecId == custtranssopen.RecId &&  
custtransopen.RefRecId == custtrans.RecId &&  
 custtransopen.AccountNum == custtrans.AccountNum  
 {  
 info(strFmt('%1', custtrans.Invoice));  
 }  
