While the current arrangement as part of the withdrawal deal is contingent on the UK/EU agreeing the whole of that deal, it is unlikely that the UK can complete Brexit with no payments made to the EU even under a no deal scenario.
This FT article suggests that the careful phrasing used by the PM Theresa May and the then Brexit Secretary Dominic Raab means that the UK will pay the EU the agreed liabilities, but will not do so on the schedule agreed during the Brexit negotiations.
What’s pretty much inconceivable is that the UK would use “no deal” to pay nothing to Brussels at all. Doubtless, the UK government could find lawyers to defend such a position in the event of no deal. But that would add one more nail to the coffin of the EU-UK relationship (on top, of course, of the economic catastrophe of no deal itself). It would set back even further the moment when the UK and EU could patch up the relationship. And paying nothing would do incalculable damage to the UK’s reputation as a reliable international partner.
During the negotiations the UK has accepted that it has significant liabilities in terms of monies owed to EU budgets. Using the lack of treaty enforcement to escape those payments would leave the UK with a reputation as a country that does not meet its obligations.