Is it possible to get IRB approval after the fact?

Generally speaking, peer reviewed journals will not publish research on human subjects that did not receive IRB approval. If a study was done without the proper IRB approval, but the study itself was ethical and clearly would have passed IRB approval if it had been properly submitted, is it generally possible to get a post-facto IRB approval that is sufficient to publish in most journals, or is the work forever "tainted"? Is the fact that post-facto IRB approval is not often considered an option because it literally isn't allowed, or because research conducted without IRB approval almost always contains ethical infirmities that would have prevented IRB approval from the start? In other words, is the requirement to obtain IRB approval truly a "You absolutely must have prior IRB approval", or is it really more like "You absolutely must not conduct research unethically, and obtaining prior IRB approval is part of Best Practices in accomplishing this, because nearly all proposals that you or I might come up with are actually unethical and we need the wisdom of the IRB to show us the light and put us on the right path. If you forgo prior approval, you are wading in crocodile-infested waters, and you will have no one to blame but yourself, not the IRB, not your mom, not your advisor, but only you yourself, if you get your leg bitten off"? To be clear, I'm not asking whether it is possible to "whitewash" unethical research to make it look like no one was harmed when in fact people were harmed, but about institutional procedural violations in otherwise ethical research. I am well aware that one of the primary reasons for seeking prior IRB approval (other than because journals expect it) is to avoid committing unethical acts, so for the purpose of this question, assume that the researchers either just get lucky or are just so competent in ethical practice that their actual research demonstrates sublime virtue (just without IRB approval). Clarification: Some people have seen fit to warn me that I am in danger of losing my job. I am not currently facing this issue. I'm simply curious as to what would happen or what typically happens in cases like these - that is, whether there are Best Practices on how to mitigate the fallout or even how serious it truly is - whether this is more of a "Calm down, it happens all the time, all you have to do is write an apology letter, sit through a five hour 'naughty, naughty bad boy, sit in the corner' lecture, be ritually spanked on the rear by your department head or the Dean, accept a 5% penalty pay cut for six months, and go through a retrospective IRB review." or a "Your career is doomed, don't dream of ever teaching or doing research ever again, you will be lucky if you ever find work cleaning floors."

It might be relevant why IRB approval wasn't obtained. Did the researchers believe, reasonably and in good faith, that it wasn't needed? Did they try to get it, but unforeseen circumstances prevented the IRB from considering the case or giving approval? Or is it the case that they knew, or should have known, that it was required, but intentionally went ahead without it?

Can we please drop the "you're going to lose your job" talk and stop speculating on what the OP's circumstances are? I received similar comments once, and it's upsetting and feels somewhat threatening.

@RebeccaJ.Stones your question was about wanting to make sure you did not break the rules, so suggesting you could get fired if you break the rules, seems unfair. Here, the rules have been broken and the OP mentions one relatively minor penalty. I thought it was important to point out there is a much larger potential penalty for breaking the rules.

It's also useful to know that the penalty could be that serious, because somebody at risk of losing their job would be well advised to stop and get advice from a lawyer and/or union rep before talking about the situation (it may well be defensible, it may well not be, but that's why you get the advice first), while somebody who just thinks they may have some unpublishable data could be make matters worse for themselves by walking into an investigation unaware of its seriousness.