Whoever wishes to join the voluntary OASI insurance scheme should present his or her request, to the Swiss compensation Office (SCO) in Geneva. This request must be sent in within one year of leaving the compulsory insurance scheme.
A Swiss citizen living abroad who is admitted to the voluntary insurance scheme is automatically insured both with the old-age and survivors insurance (OASI) and the disability insurance (DI).
When you are making your mind up about joining the voluntary OASI/DI insurance scheme, you should bear in mind that legislation on national old age and disability insurance in certain countries makes provision for reductions in pensions when the insured person has other sources of revenue, particularly foreign pensions.
Only those officials responsible for national insurance of the country concerned can give you precise information as to if, and to what extent, these sources of revenue are taken into account in the calculation of the pensions they grant.