It means there could be a "no-deal" period from January 1st.
The EU's chief negotiator Michel Barnier has warned time is running out for any trade deal with the UK to be legally in place by the 1st of January.
Even if agreement is reached soon, it would have to be legally scrubbed, translated into 23 languages before getting approval from the member states and finally ratified by the European Parliament.
One option is both sides agreeing to apply a deal provisionally, however any attempt to bypass MEPs is unlikely to go down well.
But there may not even be time for that and we could be in for a short 'no-deal' period in the New Year until any new arrangements are put in place.
The talks in Brussels between the EU and UK continue.
