.SIE File

The sie file extension is used for a Swedish open standard for transferring accounting data between different accounting and financial software produced by different software suppliers (accounting, auditing, tax declarations etc.).

SIE is a tagged text file format, not related to XML format like XBRL GL and UN/CEFACT accounting.

How to open:

It looks like that this format is common in Sweden and used in Swedish accounting program, also you can try SIE Parser to open *.sie files.

How to convert:

Probably can be used for data exchange of accounting data.