Those affected are to receive a Migration Notice letter, which will tell them when their existing benefit payments will finish.
The letter will also give them a deadline for when they need to put in a claim for Universal Credit so they can continue to receive payments under the new benefit.
People on DWP legacy benefits who do not put in a claim for Universal Credit will continue to get their payments for another two weeks after the deadline as set out in the letter.
Those on tax credits who do not make a Universal Credit claim by the deadline will see their entitlement come to an end the day before the deadline.
The rollout of Universal Credit was paused during the coronavirus pandemic but restarted last year, being carried out in stages in different parts of the country.
In May 2022, 500 households in Bolton and Medway were letters telling them they needed to migrate to Universal Credit.
The scheme then expanded to Truro and Falmouth in July 2022, Harrow in August 2022, Northumberland in September 2022, and to all postcodes in Cornwall during February 2023.
People on legacy benefits will also be switched to Universal Credit if they report a change in circumstances, such as taking up a new job or changing their address.
Legacy benefit claimants whose payments will decrease in switching to Universal Credit may receive Transitional Protection, meaning they get a top-up payment to cover the difference.
A person can also request their first Universal Credit payment in advance if they urgently need the funds to pay bills.
This amount will then be repaid as deductions from the claimant’s future Universal Credit payments.
A report published in recent weeks from Advice NI found many claimants in Northern Ireland struggled to get by when they were moved to Universal Credit.
More than half of those moving to the benefit fell into rent arrears while 47 percent went into debt or had to borrow money from friends and family.
One legacy claimant said: “Transferring is frightening and can cause a lot of worry and stress so I would need a support worker who could bring me through all steps and who I could contact when I don’t understand something.”
Advice NI called for improvements to the system including making sure claimants have easy access to the financial support available.
The group also said claimants should have real-time access to Universal Credit staff so independent advisors can flag up cases where a person urgently needs help.
A Department for Communities spokesperson told Express.co.uk: “Anyone moving to UC from legacy benefits or tax credits will have their benefit entitlement protected through Transitional Protection.
“This means that people with no change in their circumstances will not have a reduced entitlement at the point they move to UC.
“Legacy customers will continue to receive benefit payments for two weeks during the waiting time for their first UC payment (known as a two-week run-on).
“A similar run-on is already in place for those on housing benefits who move to Universal credit as a result of a change in their circumstances.”
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