If after completion or after the receipt of bids, the actual cost of any work or improvement is found to vary materially from the original estimate, or the assessment if void or invalid for any reason, or if the Village Board determines to reconsider an assessment, it is empowered, after giving notice as required in Section 3-2-5 to amend, cancel or confirm any prior assessment and notice of this amending, canceling or confirming be given by the Village Administrator-Clerk- Treasurer as provided in Section 3-2-6 of this Chapter.