"I note that UniversalCredit/UC migration (from legacy-benefits to UC) is not done for all claims/claimants (that are on legacy-benefits) on the same day. Under the FOI Act, can you please provide me with the mechanism/formula by which the SSWP (Secretary of State for Work and Pensions) identifies + decides who they issue a UniversalCredit/UC migration notice to, + when? What are the exact criteria? + who decides on these? Or is it just random?"