The hotel was of acceptable standard and well located, with an adequate breakfast. But the desk staff completely mis-handled the 19% IVA tax, so I definitely cannot recommend them. I contacted them twice beforehand about IVA handling (no reply) and then told the desk person at check-in that I was a foreigner. My Spanish isn't great but she said the price listed and charged had excluded IVA, so I left the matter until I had a chance to double-check.
The Hotels.com confirmation clearly stated that the price "includes taxes and fees", meaning that the IVA deduction should have been applied. So I showed this to the desk manager, Andreina, on checkout. With this evidence, she agreed that the price we'd been charged should be reduced by "$12" - which she said she would refund to our card the next day.
Unfortunately, this did not happen. When I emailed Andriena at the end of our travels she claimed the price on the listing didn't include IVA. I reminded her of our discussion at the desk and sent a screenshot of the Hotels.com price page showing the "includes...taxes" wording. That was a week ago - no reply at all.
This is very poor behaviour and very different from our experience in other places in Chile. I see that there have been other reviews of Hotel Nippon mentioning issues with IVA. Simply put - if you don't want to handle it properly, then don't advertise misleading prices which imply that it is included.
There are other, more honest, places to stay in Santiago.