いかんにかかわらず / いかんによらず / いかんをとわず

These three follow a noun, with or without の, and mean "regardless of": whatever the noun turns out to be, the rest of the sentence holds. They mean the same and swap freely.

The noun is one that can come out more than one way: a reason, a result, grades, nationality, the weather. What follows is usually a rule or a decision.

The endings are the negative ず forms of かかわる "to be affected by", よる "to depend on" and とう問う "to ask about", so each says the factor doesn't come into it. いかんを問わず is also written in kana, いかんをとわず. ず is the written negative, the same as ない; before the next clause it stays in the ず form, and the ない form there is wrong.

• × 理由のいかんによらない、遅刻は認められない → 理由のいかんによらず、遅刻は認められない

いかんにかかわらず or いかんによって

Without the negative, いかんによって, いかんによっては and いかんでは mean the opposite: "depending on". The two often sit in similar sentences, so read the ending.

With いかんによっては, the second half says what may happen, not what holds anyway.

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All three belong to rules, notices, contracts and formal announcements. Dropping いかん gives forms you meet more widely – てんこう天候にかかわらず, ねんれい年齢をとわ問わず – and in conversation にかんけいなく関係なく says the same.