I've seen a few words in a cursory search:

  * [在宅勤務]{ざいたくきんむ}
  * テレワーク
  * [在宅]{ざいたく}ワーク

but I'm interested in the situation where your usual place of work requires
commuting, but you are temporarily working from home just for the day, as
opposed to a situation where you are based primarily at home.
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2019-02-04T20:48:58.477
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words
What's the word regularly used to describe "working from home"?
I think any of the words you mentioned could be used that way. None of the
words you mention specifically imply that a person is always a teleworker.

You can specify that through context, as in the following dialog:

> 松村{まつむら}さんは？

  * あっ、 **今日{きょう}は** テレワークしていると思{おも}います。
  * あっ、 **今日は** 在宅勤務{ざいたくきんむ}だと思います。
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2019-02-04T21:44:16.537
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「今日はリモートで作業します。」would be a natural way to express the situation you describe.
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2019-02-06T12:57:38.000
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I asked a friend how they would ask to work from home due to say bad weather
and they said:

天候が悪く、出社困難の為、本日は在宅で仕事をさせていただいてもよろしいでしょうか？

So extrapolating from that if you were describing your own state after getting
approval to work from home I believe you would say

今日は在宅で仕事をしている。
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2019-03-08T13:40:43.000
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