I'm providing this obvious advice because as I read this sub regularly, there isn't a day (hour?) that goes by that I don't read:
“Yeah, well, uhm… he told me that on the phone…“
RECORD EVERY PHONE CALL (INCOMING and OUTGOING).
HIT THE RECORD BUTTON EVERY TIME YOU GO INTO WORK.
You cannot go back in time. You cannot record after-the-fact… after you've been ambushed by your boss, threatened, harassed, written up, fired, or even assaulted. You have to learn to be PROACTIVE.
Respectfully, it simply DOES NOT MATTER what the laws are in your state/country about two-party vs one-party notification. Record them anyway.
As a practical matter, the only time it becomes an issue is if it is presented as evidence to an agency or a court, and then the worst case is that it is dismissed as inadmissible (and even then the judge is not going to forget that they exist anyways). What's going to happen 9/10 times is that the offending party will settle a case rather than run the risk of the audio being released.
What it DOES do – when you tell someone you have a recording of them – is convey a clear message that you can prove to the rest of the world that they are a liar.
Right about now, someone wants to jump in and say “but they could sue you!” Uh, yeah, but no.
They could try to sue you, but seriously, most of the numb-nuts that people describe here and that you're documenting don't have the time/money/intelligence to follow through, and even if they retained a lawyer they are going to be advised that doing so is probably not in their best interests if they have a public image to protect.
Now for practical advice: Google “Call Recorder – ACR”. There are many tools out there, but your first hit will likely go to the one I use.
I record every single incoming and outgoing call on my phone. It requires no additional effort from me. It's all automatic. IT WORKS.
I've resolved several problematic interactions with businesses and clients when I've advised them I recorded the prior discussions, and I've only ever once had to actually play the recording. Even in that instance, I only played maybe the first 10 seconds before the person on the other end said “OK, OK! I get it. Maybe I did agree that we would…“
As for recording every day at work, the audio recording app is on every phone, and again the effort is nominal. The recordings take up little space on your phone, and if the workday was otherwise uneventful, delete the recording and free the space. Simple.
Friends have used this dealing with child custody issues, problems with medical services, repair quotes, threats/bullies against their children… the list is endless.
We live in a world where security cameras are everywhere. It's about time you learn that you need to document yourself and your interactions, too, to protect you.