The tests will reveal whether around 130 of Europe's largest banks need to raise more capital for losses they have already incurred and future crises.
The tests are designed to finally banish fears about the health of Europe's banks, whose valuation has lagged behind US peers since the region's debt crisis struck.
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The results must be published before the European Central Bank becomes the euro zone's banking supervisor on Nov. 4.
Banks will be given their results about 48 hours before publication, to enable them to review the figures and prepare any response.
Picking a Sunday publication date reduces the risk of sensitive information leaking while major markets are still trading, since the information can be given to banks after markets close on Friday evening.
"We haven't confirmed any dates around the publication of the results," said a spokesman for the European Central Bank, which is carrying out tests on the euro zone banks.
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"All we can say still is second half of October." The European Banking Authority (EBA), which is co-ordinating tests across 28 EU countries, said there was "no approved date yet".
The ECB results will include granular detail on the finances of about 130 euro zone banks and the capital actions they must take.
They will also form part of the EBA's EU-wide results, which give less detailed information about the finances and capital needs of 124 banking groups across the EU.
Both sets of results will be released simultaneously.
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