Asset acquired via PO- Once PO invoice is posted;PO number is not shown on Asset

Hi,

I have done all the necessary setup for acquiring an Asset via PO and it is working perfectly. Once the Purchase Invoice is posted, the Asset is acquired and the Financial values all are OK. Once I click on Value model, then on the PURCHASE/SALE tab

Vendor Account is appearing

Invoice Number is also appearing

but PURCHASE ORDER NUMBER is missing.

Can anybody tell me why it is missing.

regards

TP