there are certain steps required by brokerages to verify that shares are really acceptable for sale. Major brokerages seem to have stricter rules than smaller ones.
For example, I know for a fact that BofA will not allow you to sell restricted shares until ALL of the 144 rules are met...howver, there are other brokerages that may sell them for you if only SOME of these rules are met...but they then assume the risk if someone goes wrong and those shares that they sold without fully validated turn out to be phony
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