Avista Utilities plans to eliminate a $3.50 “swipe charge” on debit and credit card payments, but the fee will continue until the end of March.

Avista wanted to end the transaction charge in October, but the transition to a new payment vendor is taking longer than expected, said Debbie Simock, a spokeswoman for the Spokane-based utility.

Avista doesn’t profit from the fees, which are paid to the third-party vendor that processes the transactions. But the $3.50 charge has been a frequent source of frustration to utility customers.

The fees are more likely to affect low-income customers, including those who don’t have bank accounts, consumer advocate groups say.

About 5 percent of Avista’s receipts are collected through debit or credit card payments, and that’s expected to grow to 15 percent within the next two years. Younger customers are more likely to use debit cards to pay their bills than checks, utility officials said.

After the new vendor is operating, Avista expects to absorb the cost of the transaction fees for 12 to 18 months until the utility gets a handle on the program’s cost. The costs will be included in future rate cases, where they’re expected to add about 12 cents per month to a residential bill.

Most Avista customers still pay their bills with a check. Other ways to avoid the fees include using a bill pay service connected to a bank account, or logging into the “Avista My Account” portal on the company’s website.