A men's clothing store in Lower Hutt says it missed its Boxing Day sales target because of an eftpos crash.
Other retailers also say there were many disruptions during their biggest sale of the year.
A software fault at one of Vodafone's broadband servers near an exhange in central Wellington triggered the crash.
Vodafone says the glitch started at about 10:30am, but all machines were back on from 1pm.
One of the stores most affected was Tarocash, a men's clothing store, in the Queensgate shopping mall in Lower Hutt.
Store manager Himanui Taputu said the glitch happened at a peak shopping time and many customers were not able to complete their transactions.
She said the eftpos failure resulted in the store falling short of its Boxing Day targets.
Vodafone is to review what went wrong to ensure it does not happen again.