The annual tax bill for average single-family homeowners in Danvers is rising 4.2 percent this year. The state Department of Revenue recently certified the town’s residential tax rates for fiscal 2018 at $13.54 per $1,000 valuation, down from last year’s $14.19 per $1,000. Under the new rates, the owner of an average single-family home valued at $445,000 will pay $6,025 in taxes in fiscal 2018, or $244 more than the $5,781 average of a home valued at $407,400 in fiscal 2017, according to Steven Poulos, the town’s chief assessor. Poulos said taxes are increasing because the town spent more money this year than last. The commercial rate is $21.15 per $1,000, down from $21.83 per $1,000. The newly certified rates will take effect with third-quarter bills, set to be mailed in late December.John Laidler can be reached at firstname.lastname@example.org.