Two Westminster committees have begun a joint inquiry into the impact of welfare policy in Northern Ireland.
It will focus on Universal Credit and the two-child limit.
The inquiry is being taken by the Northern Ireland Affairs and Work and Pension Committees, and will be chaired by Conservative MP Nigel Mills.
Since a change of policy in April 2017, parents are only eligible to receive the child element of the Universal Credit payment for up to two children.
Parents continue to receive Universal Credit payments for children born before the change.
In 2016, the Stormont executive set up a £585m pot to alleviate the impact of welfare policies such as the bedroom tax and the benefit cap.
The funding is due to end in 2020 and there is no devolved government in place to secure another financial settlement.
Northern Ireland has been without a government since January 2017, when the power-sharing parties split in a bitter row.
Committee chair Mr Mills said: "Without a government in Northern Ireland, serious questions about the impact of welfare policies remain unanswered and important concerns risk being ignored."
The inquiry will also ask what the likely effects of the mitigation package coming to an end in 2020 will be; if it is feasible for Northern Ireland to have differing levels of welfare entitlement in the long term and how well Universal Credit is working in Northern Ireland.
Written evidence can be submitted to the inquiry until 24 May 2019.