Boston homeowners will face a 13% tax increase beginning in January based on city projections of pending real estate assessments.

In a Dec. 3 letter to the Boston City Council, Mayor Michelle Wu noted that the average residential property tax bill has ballooned 34% since 2023 because of declining commercial real estate values. The 13% increase in 2026 will amount to an average rise of $780 per household.

In the letter, Wu urged state legislative passage of a multiyear residential tax relief home-rule petition. The City Council and the Massachusetts House of Representatives passed the measure twice in 2024, but it was blocked from receiving a vote before the State Senate. In February, the petition stalled again in the state legislature after the City Council approved it.

Passage of the home-rule petition is needed to shift more of the tax burden from Boston homeowners to its commercial property owners, Wu wrote. This is because in contrast to residential real estate, commercial real estate is projected to see a 6% decline in assessed value next year. The tax bill for an average class A office tower would decline by 4.4%, or $210,000, compared to the 13% hike for private homes.

“The cost of housing is Boston’s most urgent issue,” Wu wrote in the letter. “Families are forgoing essentials as they pour more and more of their income into fighting to stay in their homes.”