...S&P Global Ratings assigned its '###' long-term rating to Irving, Texas' $53.2 million series 2020 general obligation (GO) refunding and improvement bonds, $13.4 million series 2020 certificates of obligation, and $3.1 million series 2020 tax notes. At the same time, S&P Global Ratings affirmed its '###' long-term rating on the city's GO debt and certificates of obligation outstanding. The outlook is negative. Revenue from Irving's ad valorem tax, levied within the limits prescribed by law on all taxable property within the city, secures the city's GO bonds, certificates, and tax notes. The series 2020 certificates as well as existing 2017A certificates are additionally payable from surplus revenue of the city's water and sewer system, limited to $1,000. Given the limit on the revenue pledge, we rate the certificates based on the limited-tax GO pledge. The series 2017B certificates of obligation are further secured by pledged revenue, consisting of state sales and use taxes, state hotel...