Landlords have about two weeks left to register their rental properties with the city, part of an annual program that helps Boston officials assess the vast numbers of private rentals within their borders.

The Inspectional Services Department assumes about 122,000 private rental properties are in use in Boston, according to ISD Commissioner William Christopher. That’s how many are registered with them, at any rate, but it fluctuates every time a landlord adds, shrinks, converts, or combines units.

“Essentially what it is is we’re learning the profile of the housing stocks in Boston,” Christopher said. “Under this ordinance, we’re able to get confirmation from owners on number of units, the general condition of the building.”

The ordinance includes a unique feature requiring specific inspections for private buildings with seven or more units, excepting rooming houses, dorms and lodging houses with a valid lodging license. This latter group is categorized differently, and if included in the private unit estimate would raise the number to around 160,000.

Mandatory inspections “give us a little more strength to get into units to get a look,” Christopher said.

An operating assumption that “there’s a minimum level or quality that should be ascertained in every unit” drives the inspectional portion of the ordinance. Inspectors check the residences out for sanitary code compliance, and if it does not meet those standards, inspectors write violations with the goal of getting the problem fixed as soon as possible.

Registration for this year must be completed by July 1. Rental property owners can find forms and resources at the rental registration section of the Inspectional Services Department page on boston.gov.

Landlords pay an initial $25 fee and subsequent $15 for each registered unit, maxing out at $2,500 per building and $5,000 for an apartment complex.

The original rental registration program came into effect in the 1980s, rejuvenated as an ordinance in 2014 and tweaked a few times since. Changes included waiving or reimbursing the fees for seniors, and removing the inspection requirement for owners with six or fewer units, though they must still be registered.

Ten inspectors are dedicated to the rental registry program, along with a supervisor and administrative staff.

Every unit is inspected at least once every five years. Owners in good standing with a good track record of code compliance can apply for a five-year exemption on the inspections.

Ordinarily, inspectional services pops into units at random, sometimes based on complaints, visual cues, or the like. The landlord is responsible for coordinating access to the property.

“The right of entry laws still stands, and that’s always an issue with us,” Christopher said, “but it’s something that we really respect.”

Residents can let inspectors into a home, but only into their areas and any common space, Christopher said. A person occupying a private portion of a home has control over whether inspectors can access that portion.

Tenants are given 30 to 90 days notice of the inspections, some of which will inevitably be rescheduled. The online portal means that almost every step of the registration process can be completed through the website.

“We’ve tried everything we can to make this process simple,” Cristopher said.