“不咎”常见的英文表达是 “not to blame” 或 “not to hold accountable”，具体使用需结合语境：
1、 “既往不咎”（to forgive and forget past mistakes）
英文：Let bygones be bygones.
或：We won't hold your past mistakes against you.
例句：既然他已道歉，我们就既往不咎吧。（Since he has apologized, let's just let bygones be bygones.）
2、 “不追究责任”（not to hold someone responsible）
英文：We won't blame you for this.
或：You won't be held accountable for the mistake.
例句：公司决定对这次失误不追究责任。（The company decided not to blame anyone for the error.）
3、 “宽宥不咎”（to pardon without punishment）
英文：To pardon without punishment.
或：To show mercy and not punish.
例句：他因自首而得到宽宥不咎。（He was pardoned without punishment due to his confession.）
总结：若强调“不追究过错”，用 not to blame 或 not to hold accountable。
若强调“既往不咎”，用 let bygones be bygones。
若强调“宽宥”，用 pardon 或 show mercy。
根据具体语境选择最贴切的翻译即可。