The electronic services provider claims the most vulnerable members of society rely on its terminals to pre-pay their gas and electricity bills and if local stores are allowed to close millions may be left without heating.
Consumers made 1.8 million transactions pre-paying energy bills via PayPoint terminals in local stores on Christmas Day, Boxing Day and New Year's Day, it said.
"Many of those who rely on PayPoint to pre-pay utility bills are the most vulnerable in society," said PayPoint spokesman Peter Brooker. "Many need to pay their bills in cash so this service is a lifeline. C-stores are ideal for this because many work for such long hours and are often open on bank holidays."
Between 2000 and 2009 the number of c-stores has decreased by 9.9% to 41,808, according to the latest figures from IGD and The Grocer's publisher William Reed Business Media.
C-stores were coming under "enormous pressure" and the government needed to do more to help them stay open, said Brooker.
The timing of the VAT rate increase, which came into effect on 1 January, had proved particularly problematic for c-stores as it created more work in one of their busiest trading periods, he added.
The letter was sent as part of the Better Local Living campaign launched by PayPoint last year to raise awareness of the services it provides in local stores.