In the case you outline, interest on the amount owed would apply at a punitive rate of .0219% per day for the 14 months since death.
I asked revenue for an extension, explaining that the house sale was going through but due to the pandemic it was delayed and would not be complete within a year of death.
Revenue replied stating that they are the collection agents for the HSE and could not grant an extension to the collection timeframe and are bound by legislation to charge interest from the date of event.
But the reply went on to say, once the principal amount is paid, the interest on late payment can be appealed and revenue takes a fair and pragmatic view and judges each case on its own merits.
From this response it appears there is some flexibility to waive the interest for genuine cases though I have no idea how long beyond the year you might get away with.
In this case there was also no cash in the estate, some of the beneficiaries then decided to pay revenue from their own funds before the due date and were refunded from the house sale proceeds before distribution.