Question on Document Summarizationin FI for tax lines

Dear Experts,

This is my first post so please forgive me if any rules have been broken inadvertently. my question is regarding document summarization in FICO. My company has a requirement of a tax report line itemwise with article code & description updated in each line item alongwith tax base amount, tax amount and rate. I tried to extract data from BSET but found that for sales documents , one tax line per rate is being posted, i.e. if I had 100 articles in the document and 3 tax rates, BSET is showing only 3 lines(one per tax rate). The document related to purchase is however showing separate line per article in BSET. As a result I am having to generate the sales data from the SD tables(VBRK/VBRP/KONV). My question is , is this standard SAP behaviour or am I missing some config? We are in ECC 6.0

Regards,

Rudra