The Ozaukee County Treasurer's office advised us that the USPS instituted a nationwide change as to when a postmark is affixed to incoming mail in August of this year. Instead of postmarks being affixed when the item is first touched by the Postal Service, postmarks are now stamped at regional sorting centers, so the postmark could be several days after you put it in the mailbox. In other words, don't wait until the last day to mail it, or it may be late. Or, better yet, use our drop box or stop in with your payment to ensure we receive it on time.