I wouldn't generally do one for husband and wife who trade in partnership together, but it does really depend on the asset and liability postiion of all estates.
Interlocking IVAs seek to take two IVAs - usually for husband and wife - and pool the creditors from both cases together, repaying them from a combined disposable income, or asset realisation. This procedure should only be used if one or both of the parties could not propose entirely separate IVAs - which should always be the case if affordability dictates.
