JEFFERSON CITY, Mo. (AP) — The cost of prepaid cellphone service in Missouri slightly increased on Tuesday as the state joined most of the rest of the country in charging a tax to fund 911 emergency call centers.

But not all customers will pay the extra charge, because 18 counties and one city have exercised an opt-out provision in the new law.

The cellphone tax is one of several state laws taking effect with the new year that carry financial implications. Missouri also is cutting the individual income tax rate by one-half of a percentage point to 5.4 percent but is offsetting that by reducing...