The housing delivery test aims to measure how effectively each local authority is delivering housing. It works by comparing each councils' level of housing delivery - using the the net additional dwelling figures - over a three-year period to the total number of homes required.
The test results for the 2016-19 period were published last week, having been postponed for three months following the December general election. They are the second annual test results that the government has published.
Under the National Planning Policy Framework (NPPF), all councils have to demonstrate a five per cent land supply buffer as standard, in addition to their required five-year supply of deliverable housing sites.
But under the test, authorities delivering under 85 per cent of their housing requirement will have to provide a "buffer" of sites for 20 per cent more homes than are needed to meet their five-year target.
The penalties take effect from the moment the results are published, according to the 2019 National Planning Policy Framework (NPPF).
The test results show that 109 authorities - exactly 33 per cent - scored under 95 per cent and face a penalty, which means that at minimum they will have to produce an action plan showing how they will improve their housing delivery performance over the next year.
Of these, 83 authorities fall under the 85 per cent threshold will have to find the additional 20 per cent buffer with eight of these facing the most severe penalty, the NPPF's presumption in favour of sustainable development.
Of the 83 that will be required to show the 20 per cent buffer, 63 already have a 20 per cent buffer following the 2018 test results.
But 20 of them previously had a five per cent buffer, having scored 85 per cent or more in the 2018 test, and now have to add 15 per cent more planned homes to their land supply (see below).
Some 15 of the 20, exactly 75 per cent, are authorities in the greater south east (London, South East or East of England), with just one (York) from a northern region and two from the midlands.
Planning research in December estimating the results found that 19 councils would have to increase their land supply buffer under the test. One authority on our list was not included in the actual list above, with two further authorities in the latter group but not in our estimated version.
Full details of all the 109 councils that are being sanctioned under the test, including their housing requirement and delivery figures, can be found here.