The "within 28 days of a positive result" figures are a method of gathering data quickly, whilst it may capture a small number of people that died from totally unrelated reasons to covid, it will also miss some that weren't tested, the figure since mass testing has been available, are similar to the number of people with covid on their death certificate, suggesting it is a good proxy.
There's some lag in reporting the figures for 'covid on their death certificate', but they are on the dashboard* for all to see, but that lag means only fairly accurate 7-day averages are currently only going up to 18th June.
Death certificates are filled out by medical professionals who may take covid test results into account, but are not required to include covid as a cause of death if it isn’t relevant to the death of someone, so will exclude non-covid related deaths, such as being run over.
* scroll down here -
https://coronavirus.data.gov.uk/details/deaths
Its been a while since I went on about this so I'll provide some indicative figures again now. And as usual I will state that I would expect death certificates to underestimate Covid deaths too, although the extent of that will have varied over time.
Figures are for the UK as a whole.
Where I say '60 day deaths' this is actually me replacing the figures for England dying within 28 days of a positive test, with figures for England within 60 days of a positive test. I cannot repeat this for the other nations as the data isnt available or they used other criteria in the first place.
Dates I'm using:
Wave 1 - March 2020 till end of August 2020.
Wave 2 - September 1st 2020 till end of May 2021. (Was actually 2 waves rolled into one in most places, pre-Alpha and Alpha, but cant separate them properly)
Wave 3 - June 1st 2021 onwards.
Wave 1:
28 day deaths: 41,648
60 day deaths: 45,607
Death certificate deaths: 57,893
Wave 2:
28 day deaths: 86,210
60 day deaths: 100,433
Death certificate deaths: 95,799
Wave 3:
28 day deaths: 1,314
60 day deaths: 1,574
Death certificate deaths: 966 (lags further behind the other measures)
Totals so far:
28 day deaths: 129,172
60 day deaths: 147,614
Death certificate deaths: 154,658
My figures may vary a little from those shown on dashboards due to the way I use figures by date of death rather than by reporting date, and other tedious details.
I would also factor in that in the first wave it was possible to use excess deaths as a guide, and there may have been around 65,000 of those in that period. We could argue for a long time about how many of those were Covid deaths, but I would certainly use that figure to suggest that death certificate figures did not capture the full death burden during that wave.
Overall when combining different figures, I would not like to claim that there have been less than 160,000 Covid-related deaths in the UK so far.