A county initiative meant to straighten out the estimated 500 short-term rentals not remitting Marin’s transit occupancy tax is being launched this week. Starting today, the county will mail notices to operators announcing a 30-day window to come into compliance. In exchange, county tax collector Roy Given is allowing those operators—who represent about half of all the short-term rental operators he estimates exist in Marin—to either pay the amount of back taxes they owe since March or prove that they are not in fact operating a rental. As online vendors like Airbnb have gained prominence in the short-term rental space, they have also gotten better at hiding information from “someone like me, who has to enforce the collection and remittance of T.O.T.,” Mr. Given said. County supervisors, concerned that many rentals were not registered, hired Host Compliance, a company that monitors short-term rental compliance, in December 2017. The company monitored over 25 websites to identify operators and has estimated the balance that each owes to the county. Should those operators ignore the compliance window and fail to register for a business license and pay their past balance, Marin will file a tax lien (a form of security interest) against them. Previously, the county had to take individual operators to small claims court if it suspected that they were failing to remit the tax, a method Mr. Given said was not particularly effective. This is not the first time the county has offered amnesty: In 2013, non-compliant operators were given three months to come into compliance. Roughly 70 took part in the program, which excused any taxes owed prior to October 2013. Unfortunately for them, operators who did not take advantage of the amnesty may now find themselves facing a compliance audit and a requirement to pay their outstanding balance for the past three years. At a county workshop on Nov. 14, officials showed participants how to register and report their T.O.T using a new online service. Some were surprised to learn that local operators who use Airbnb are still responsible for registering and reporting their rental activity to the county. “They don’t have to pay me any money,” Mr. Given explained, “but they have to tell me how much they rent their rooms for so I can compute the T.O.T. so I can make sure Airbnb is remitting the right amount.” The final leg of the initiative aims to have all online platforms remit the tax on the operators’ behalf. Some platforms—like Airbnb—already do, but others do not, creating confusion for operators and the county alike. Thanks to data collected by Host Compliance, Mr. Given said, he is “now in a position where I’m able to put the county’s best foot forward to identify individuals and enforce collection.” There are currently 530 registered short-term rental operators, and he expects that number to nearly double if non-complying operators begin to comply. “What I want people to do is the right thing,” he said. Proceeds from the T.O.T. help fund various projects across the county, though West Marin’s recently approved hike in the tax will be earmarked for local affordable housing and firefighting.