In the USA:
Companies have four business days to file a Form 8-K for the events specified in the items in Sections 1-6 and 9 above. However, if the issuer is furnishing a Form 8-K solely to satisfy its obligations under Regulation FD, then the due date might be earlier. (Issuers with questions concerning compliance with Regulation FD should consult with counsel or the SECs Division of Corporation Finance.)
https://www.sec.gov/fast-answers/answersform8khtm.html
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