It is best to use the various invoice history files as they contain the actual cost.  Sales order files do not contain actual cost because if you have FIFO, Lot or Serialized items you will not know actual cost until invoicing.

Thank you for the reply.

Do you mean the UnitCost field in the AR_InvoiceHistoryDetail?

Sales Orders are not actual transactions, they are potential transactions (and you cannot get reliable costs from SO tables).  Nothing is "final" until the associated invoice is posted (including costs, as BigLouie mentions). 

Posted SO invoice data is in the AR_InvoiceHistory* tables. 

UnitCost in the AR_InvoiceHistoryDetail table is the best number (and it should match the associated entry in IM_ItemTransactionHistory).

Thanks Kevin.

How can I join the two tables of AR_InvoiceHistoryDetail and SO_SalesOrderHistoryDetail because I need to get the job cost referenced by SO#? Is it SalesOrderNo in AR_InvoiceHistoryHeader?

But why there's no SalesOrderNo in AR_InvoiceHeader but in AR_InvoiceHistoryHeader?

Link AR_InvoiceHistoryHeader to AR_InvoiceHistoryDetail using InvoiceNo and HeaderSeqNo.  Use the header table's SalesOrderNo.

There is a table SO_ARInvoiceHistoryLink that helps you link invoice history to SO details.

Appreciate yours Kevin.

So for the knowledge, what is the UnitCost in the SO table? Cost at the time creating the SO?

It is an estimate with logic which differs based on Valuation.  StandardCost, LastCost, AverageCost...

Thank you.