FRANKFURT, Sept 2 (Reuters) - German exchange operator Deutsche Boerse is due to announce new entrants to the blue-chip DAX index on Friday, part of the index's biggest ever overhaul https://www.reuters.com/article/us-deutsche-boerse-dax-idUKKBN2840J0.

The index will expand to include Germany's 40 largest listed companies, from the 30 biggest currently, effective Sept. 20. Prompted by the Wirecard accounting scandal, Deutsche Boerse has also tightened criteria for inclusion in the index.

Here's an overview of the changes:

INDEX MEMBERSHIP

* The DAX expands to 40 from 30 members, and the mid-cap MDAX index shrinks to 50 from 60 members. The small-cap SDAX remains unchanged at 70 members.

* Analysts see as possible candidates to join the DAX Beiersdorf , Airbus, Zalando, Siemens Healthineers, Symrise, Porsche SE , Sartorius, Brenntag, Hellofresh and Qiagen

MEMBERSHIP CRITERIA

* As of December 2020, all new DAX candidates are required to have positive earnings before interest, taxes, depreciation, and amortisation for the past two financial years.

* As of March 2021, all companies in any DAX index are required to publish audited annual financial reports and quarterly statements. After a 30-day warning period, failure to comply results in immediate exclusion from the index.

* Also as of March 2021, index members must comply with the recommendations of the German Corporate Governance Code that require the formation of an audit committee in the supervisory board. There is a transition period for existing members.

* From this year, the indexes are scheduled for review twice a year, in March and September. Previously, the review took place once a year in September.

* From this month's review onward, membership will be based on market capitalisation, while exchange turnover will no longer play as significant a role. (Reporting by Tom Sims and Anika Ross; Editing by Jan Harvey)