Under prevailing EU regulations , the mandatory national social security system (‘SSS’) applicable to a worker active in the EU  in cross-border situations is generally based on the (habitual) place of work. Due to COVID-19 measures, quite a number of workers have now been required or recommended to work from home, either for part of their working time or for their full working time.
This means that in such situations, the habitual place of work may de facto have changed dramatically in comparison to any pre- COVID-19 era. For instance, an employee usually occupied full time in Paris for an employer there, but having his residence in Brussels, may have been asked (and has continued) to work from his Belgian home either full time (e.g. since 16 March, the start of the lockdown) or for part of the week.
Applying the basic principles of such regulations, taking into account the effect of the home work would mean that the individual would become subject to a different SSS in many situations, including in both examples: working full-time from home in Brussels or for at least 25% (in his home country) would render the Belgian SSS applicable rather than the French SSS.
In the meantime, the Belgian social security authorities, alongside many of their EU colleagues (in France, Germany, Luxembourg and Denmark for instance), have taken the decision not to take into account the particular COVID-19 home work for these purposes. In other words, for purposes of applying the appropriate national SSS, the authorities have decided to make abstraction of the temporary change in working patterns and in particular the home working due to sanitary reasons. In the example, notwithstanding the home work from Brussels, the employee at stake would thus remain subject to French SSS. At this moment, it is unclear whether – but quite likely (and certainly recommendable) that – all member states will adopt the same administrative position on this issue.
This administrative approach remains in effect as long as the home work is COVID-19 related or based on mandatory working patterns in the respective member states. For Belgium, the administrative decision is valid until the end of 2020. In itself, this may raise a number of practical difficulties, not in the least because there is no EU-wide decision-making process nor coordination of what is a mandatory/recommended COVID-19 related home work pattern. In other words, as is the case already today, some member states impose home work (sometimes even for specific parts of their territory, such as the Antwerp province in Belgium), whilst for others only recommendations or suggestions are in place. Also, as the ‘new normal’ pattern of work will definitely include a far wider spread of home work in the business community, until when will home work be ‘COVID-19 related’ and from when will home work become a free and deliberate work organisation strategy of companies?
These and other issues may have desired (and sometimes undesired) effects of shifting the applicable mandatory SSS from one member state to another, with all consequences in terms of coverage, cost, funding, protection and benefits. Companies with staff operating on a cross-border basis would therefore be well advised to (i) check if and how current COVID-19 related home work patterns might in theory affect the applicable SSS (bearing in mind the administrative position taken), (ii) examine and assess to what extent the continued use of home work (beyond the current COVID-19 situation) may affect the applicable SSS, including effects on labour cost, social protection and benefits, and (ii) finally make a cost-benefit analysis of such potential change of applicable SSS for all parties involved (employer cost vs employee benefits).
As the current COVID-19 situation has fundamentally changed the way we work, this will clearly have an impact beyond the current crisis. Concepts like 'locus of employment' which have a key significance for employment, social security and tax laws will have a different and far more sophisticated content. The scope of required reform and amendment to regulations at EU and bilateral level will therefore be immense.
We will come back to these wider issues in due course.
 EU Regulations 883/2004 and 987/2009 on the co-ordination of social security systems.
 Including the European Economic Area and Switzerland.