I received more money than I was supposed to have so please offset it for next time.
I received more money than what I was supposed to have so you can make adjustments in the next calculation.
ご質問ありがとうございます。
「(お金)を多くもらってしまったので次回相殺させてください」は英語で「I received more money than I was supposed to have so please offset it for next time.」と言います。
また、別の言い方で「I received more money than what I was supposed to have so you can make adjustments in the next calculation.」に言えます。
これは日本語だと「お金を多くもらってしまったので次回の計算で差額を調整してください」という意味です。
ご参考になれば幸いです。