Partnership

I have tried the Self Assessment helpline but no technical advisers are available! They suggested I called back first thing in the morning or late in the evening (when they are not so busy) but I would like an answer today, if possible, so I can contact this client.

A (potential) client has been in partnership for a few months but not registered the partnership. The partnership existed Nov 09 to May 10 (crossing 2 tax years) and this person has then continued in self employment. I am not sure of the status of the other person but assume (for now) they are still self-employed.

Is it best to register the partnership, or would it be acceptable to split the income/expenses 50/50 on the self employment pages? The joint income is not CIS Income (work for private householders). It isn't possible to treat one of them as a subcontractor to the other, as they would then be in breach of CIS.

Has anyone any experience of HMRC's viewpoint on this? It would save my client money, and speed up preparation of the tax return if we could bypass registering the partnership.