Universal Credit claimants could be underpaid their benefits, Martin Lewis' website, MoneySavingExpert, has warned.
It explained how information about your earnings could end up in the wrong assessment period due to a "flaw".
The Department for Work and Pensions (DWP) communicates with HM Revenue & Customs (HMRC) to work out the benefit.
READ MORE: Money expert Martin Lewis lands Good Morning Britain job as cost of living crisis grows
HMRC matches up information with your NI number, but the employer submits the details which could cause delays.
Now MSE has warned this delay could mean your earnings information ends up in the wrong Universal Credit assessment period.
![Wallet full of UK money](https://i2-prod.dailystar.co.uk/incoming/article27830720.ece/ALTERNATES/s615b/0_UK-sterling-pound-notes-in-walletjpgrsal.jpg)
Either you've earned more than you did, or you've been marked down as working less, in which you'd have to tell the DWP.
MSE estimates roughly 1% of worker's earnings information is submitted without a National Insurance number each month.
This means around 20,000 people, out of the 2.2million working Universal Credit claimants, could be impacted by this issue.
If you're worried, the first thing you should do is check your online Universal Credit account.
Martin's website says you're more likely to be affected by a payment issue if:
You get paid weekly, fortnightly, four-weekly, or irregularly
You didn't have to provide a NI number when you gave your employer your payment information
You have pay days that fall very close to the end of your universal credit assessment period
You've just started a new job
To fix the problem you'll have to raise the issue with the DWP so they can look into it.
You can either do this through your online account, or call the helpline for free on 0800 328 5644.
![Martin Lewis](https://i2-prod.dailystar.co.uk/incoming/article27830725.ece/ALTERNATES/s615b/0_Martin-Lewis-calls-on-Business-Secretary-to-apologisejpgLewis.jpg)
Make sure you have bank accounts and payslips to hand to prove your earnings.
If the DWP can't fix the issue, ask for a "mandatory reconsideration" which you can do over the phone or by filling out a CRMR1 form.
You do have one month to appeal if you're not satisfied with the outcome.
A spokesperson said: "DWP and HMRC work closely to support and inform employers who report earnings, to emphasise the importance of timely reporting via the RTI system, to reduce any issues.
"HMRC has updated its guidance to reiterate to employers the importance of reporting accurate dates and the impact on payment cycles."
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