Los Alamos County property tax bills for 2009 were mailed to property owners in November.
The first half installment was due Nov. 10, and becomes delinquent after Dec. 10.
Payment must either be made in person at the 311 Customer Care Center by 5 p.m. Dec. 10 or postmarked by midnight that same day to avoid late payment penalty and interest charges.
The 311 Customer Center is open from 8 a.m. to 5 p.m. Monday through Friday at 901 Trinity Drive. Payments should be mailed to P.O. Box 99, Los Alamos, N.M., 87544.