Around half a million people have been denied child benefit due to a technical issue at HMRC.
HMRC said it was working to resolve a batch processing issue which meant around 30% of payments due on Monday were not made.
Many parents took to social media to complain about falling behind on payments, with some saying they could no longer buy food or afford their children's bus fares.
HMRC has asked customers not to contact them and said more information will be provided on social media when it becomes available.
Britain's tax authorities, which administer child benefit payments, have said the outstanding payments will be made but have not yet said when.
You can claim child benefit if you are responsible for raising a child under 16, or under 20 who is in approved education or training.
Only one parent can receive a payment per child, but there is no limit to the number of children who can claim.
Payments are typically made every four weeks and arrive on a Monday or Tuesday.
“We regret that some customers have not received their child benefit payments as scheduled and are working urgently to resolve the issue,” HMRC said in a statement.
The company said the issues that caused problems on Monday would not affect payments scheduled for Tuesday.
Anyone affected by the technical issues can file a complaint online.
