undercharge
🇺🇸
/ˌʌndərˈtʃɑːrdʒ/
🇬🇧
/ˌʌndəˈtʃɑːdʒ/
to charge someone less money than they should be charged for something, often by mistake
The shopkeeper realized he had undercharged the customer for the groceries and quickly corrected the mistake.