Poison pill - pre or post offer?

The books and questions claim poison pill to be pre-offer defence that cannot be used after the offer is put on the table.

However everywhere in the market I read poison pill is made after the offer.



So where is the truth?

For the exam, go with the CFA book.

I don’t think they mean that you cannot use it post-offers, only that it is more effecive as a pre-offer strategy to deter hostile takeovers.

poison pills are implemented in advance of a takeover. I guess they are actioned once a takeover occurs (e.g. with dilution) but they are a pre-takeover strategy