I have to pay any additional charges on my electricity bill once a year.
I have to pay any outstanding charges on my power bill once a year.
この場合、次のような言い方ができます。
ーI have to pay any additional charges on my electricity bill once a year.
「年に一回、電気代の追徴金を払わなければいけない」
to pay any additional charges で「追徴金を払う」と言えます。
electricity bill で「電気代」
ーI have to pay any outstanding charges on my power bill once a year.
「年に一回、電気代の追徴金を払わなければいけない」
to pay any outstanding charges で「追徴金を払う」とも言えます。
power bill で「電気代」
ご参考まで!
Besides my regular electricity bill, I need to pay additional charges to my electricity company once a year.
ご質問ありがとうございます。
この場合、「年に一回、追徴金を[支払わなくてはいけない](https://eikaiwa.dmm.com/uknow/questions/47398/)。」と言いたいなら、英語で「Besides my regular electricity bill, I need to pay additional charges to my electricity company once a year.」と言えます。
ご参考になれば幸いです。