The recently published withdrawal transition agreement with the EU says little directly about VAT.  However, it has been agreed that the UK will effectively remain within the EU Customs Union until 31 December 2020 and so this will give businesses more time to adjust to the new customs arrangements (whatever they are) that come into effect on 1 January 2021.

The transition agreement states that the EU VAT Directive in relation to goods will continue to apply to the UK until 31 December 2020, although this has not been agreed in detail.  There is no mention of services or of the VAT MOSS scheme but it seems likely that the current arrangements will continue during the transition period.

As with any matters relating to Brexit, we cannot be absolutely certain that there will be no radical changes next March until the agreements between the UK and EU have been signed.  Businesses that trade regularly with the rest of the EU should continue to watch out for any announcements on customs and VAT arrangements.