Once the plat is finalized, the next step is to collect signatures and notarizations. Signatures will have to come from all of the land owners, whether they are corporate entities or individuals. If the land owners consenting to the plat are married then the marital status will have to be identified on the plat, and the spouse will need to sign as well. The city council or town board will likely have to sign, possibly the city, township, or county planning commission, possibly the city attorney as well (the roster of necessary signers varies depending on the jurisdiction, to be sure to check on this in advance). The county surveyor and the surveyor creating the plat will also have to sign the plat.
The county auditor or treasurer will have to sign, and in so doing they will certify the taxes payable for the land affected by the plat. Finally the county recorder or the county registrar of deeds will have to sign certifying that the plat was filed among the public records.
Each jurisdiction will differ somewhat as far as what parties will have to sign to consent to the plat. Be sure you are checking for those requirements before creating the proposed plat and submitting it for review.