Line Source Post Import of manual tax lines

Hi ,

Post import of manual tax lines , the line_source for few invoices  is ETAX and for few its IMPORTED .

Please help me to understand the reason. Also will there be any change in further processing of the invoices having different line sources for tax lines .

Following is the observation for imported tax lines

LINE_SOURCE	Tax Classification Code
ETAX	Tax Classification Code is NULL
IMPORTED	Tax Classification code is not NULL .Same as provided in AP_INVOICE_LINES_INTERFACE.

Thanks

Shripad