England took a 2-0 lead, just as they did in the ODI series that preceded it, ahead of Sunday’s final game of their first tour in Covid times.
With Katherine Brunt absent ill, Freya Davies stepped up, taking her best figures for England, four for 23, while there were also superb bowling performances from Nat Sciver (two for 25) and Sarah Glenn (two for 23).
That limited New Zealand to just 123 for nine in their 20 overs, and Beaumont helped England knock the target off with six wickets and 16 balls to spare.
England fell to 30 for two having lost Danni Wyatt and Sciver, but captain Heather Knight joined Beaumont to share 83. Both fell with the finish line in sight, but the job was done.
Beaumont, the top-ranked ODI batter in the women’s game, made 63, her fourth half-century in five innings on tour.