Filing a mechanic’s lien requires that you actually take your mechanic’s lien form and record it in the proper recording office in the county where the project’s property is located. Most county recorders will accept documents for recording by regular mail, overnight delivery or in-person hand delivery.
In most instances, sending your lien for recording by any of these methods will be fine. As with everything, however, there are exceptions.
Back in 2008, I wrote a blog post here warning about delays and backlogs with certain California recorder offices. At the time in Los Angeles, for example, liens sent for filing by mail could get held up and not recorded for more than six weeks! Practically speaking, this means you could send a lien for filing with 5 weeks to spare on your deadline, and still not file it in time.
Unfortunately, the backlog in Los Angeles persists even today. And there are a host of other counties across the country with backlogs from a few days to a few weeks, and you should be very careful about sending them a lien for recording via regular mail or overnight delivery. In these counties, sending the lien with a courier is the best bet.