People saving with NatWest could win £1,000 this summer if they turn on a “round ups” feature on their account.
The bank said it will award 10 customers £1,000 each.
The round ups feature rounds up the cost of a purchase to the nearest pound and the spare change is automatically paid into a chosen savings account.
The competition runs until June 30, with winners drawn at random on July 14.
The prizes are aimed at those turning the feature on in the mobile banking app during the period of the competition.
NatWest has also introduced a “double ups” feature, enabling customers to automatically move double the spare change into their savings. The account opening age has also been lowered from 18 to 16 years old.
The bank’s digital regular saver account pays 3.25% on balances up to £1,000 and people can put in up to £150 each month.
Some other providers also run competitions, for example Nationwide Building Society has a member prize draw.