The city’s Inspectional Services Department (ISD) has announced a newly revamped rental registration ordinance that will require all privately owned rental units to be registered with the city of Boston on an annual basis.

According to ISD Commissioner William Christopher, the ordinance was actually put in place in 2013 by the city council but has been “retooled” since Mayor Marty Walsh took office in 2014. Now, he said, the ordinance will require more information from owners in order for ISD to create a database of the city’s estimated 160,000 rental units.

ISD’s renewed effort at transparency and enforcement comes in part as an effort to ensure that rental units are safe and in compliance with the state sanitary code.

“With the mayor’s position on housing, we’re trying to analyze what our housing stock looks like in the City of Boston,” Christopher said. “Our hope is to use this database so that we can have accountability and so that we know who owns what building and where.”

Registration is relatively simple. Owners are asked to identify themselves, supply their contact information and provide a description of their rental properties. Owners will be required to pay an initial registration fee of $25 per unit and $15 per unit each year thereafter, with a maximum possible fee of $2,500 per building and $5,000 per complex.

Properties with six or fewer units, one of which is occupied by the owner, will not have to pay the registration fee, but will still be required to register each year.

Christopher said that ISD then plans to inspect all registered units in the city of Boston within the next five years. In the past, this part of the ordinance was difficult to enforce because occupants could deny ISD access to rental units for inspection, he said. But the revamped rules will allow ISD to be more proactive in its approach by scheduling inspection appointments with occupants and owners.

“We’re trying to work everything together so we can have a unified way of looking at units throughout the city,” he said.

The registration period opened on April 19 and property owners will have until July 1 to comply. ISD’s online registration portal was out of service as of May 3, but Christopher said that registration can also be completed by mail or in person at ISD’s Housing Division located at 1010 Mass Ave. For more information or questions regarding the ordinance call 617-635-1010.