People who claim Universal Credit will not get the benefit over the festive period, it has been reported.
Those who are in work and get paid each week may receive no payment or a reduced payment as there are five weeks in December.
This means that their monthly income will be too high to qualify for the benefit.
The Department for Work and Pensions said only a 'minority' of people will be affected.
But the BBC reported it will hit some of the 67,000 claimants who are in work and get paid weekly.
Kayley Hifnell, from Citizens' Advice, told the BBC: 'People need to know that if they're getting extra income in one month... it may stop their universal credit payment, and that they then subsequently need to put in a new claim to make sure that they continue to get those payments.
'If you've got extra money in the month, don't necessarily bank on the fact that your universal credit is going to stay the same, because it could change it either in this month or the next.'
Unite, the trade union, recently protested against Universal Credit outside the constituency office of Portsmouth North MP Penny Mordaunt.