Yes, they tally them daily up to tea time. The case and deaths data is always from the day before. As it is for all four nations.
And many of the deaths and cases are actually from previous days up to some weeks before as my detailed day to day numbers for England I post here daily afterwards show.
They are just deaths announced today and separate lists are kept of that number (the one the news tonight reports for the UK added together) and a constantly updated list ascribing the deaths to the actual day of death.
These tend to end up quite different after a week or two as I note from time to time when posting that data.
But - as with the chaos on the testing last night - they are just reallocated to different days and the total we are at remains the same (bar rare exceptions were deaths are removed later if redefined).