Council Tax Benefit
Access to these benefits was previously restricted to those who proved that they are "habitually resident" in the UK or Ireland.
In other words, you could not just turn up in the UK and automatically claim a benefit - you had to prove that you normally lived in the country, though there were more flexible rules for Irish citizens.
The new rules say that migrants from new EU states will need to prove not only do they normally live in the UK, but they have a right to live here too.
That right of resident is based on the economic status - and citizens of new EU states only obtain that right if they are working or self-employed.
"Economically inactive" - jargon for students and pensioners, have a right to abode providing they can prove they are self-sufficient.
How does this differ to other migrants?
Migrants from other nations around the world can only come and work in the UK if they have been separately cleared for a work visa and given "right to remain" by the Home Office.
This leave to remain in the UK does not include an automatic right to claim benefits, despite what many people think.
Furthermore, asylum seekers do not have the same rights. They are not allowed to work while their cases are being considered and their state support is a third lower than standard benefits. If they are given refugee status or leave to remain for other reasons, they can then seek work.
The government announced in March it is going to stop giving this group back-dated full benefits for the period while they were waiting for a decision.
How to benefits in the UK compare to other EU member states?
This is an extremely complicated area because national welfare systems are neither harmonised nor directly comparable.
A benefit available in one country may not exist in another. Eligibility in one place does not necessarily translate to eligibility elsewhere.
However, the European Union has made a stab at it and come up with a league table of "social protection" across the continent.
The average spending on benefits across Europe (excluding new EU members) is 27.5% of GDP.
But within that average there are huge differences.
Using a measure which calculates how much spending power a benefit payment truly provides in each country (purchasing power parity) the league table shows Luxembourg has the most generous welfare system, followed by Norway (not an EU state) and Denmark.
The UK is the 12th most generous spender on welfare by this measure.