This question has been posed due to a comment in another post questioning the ability to alter the profit sharing split retrospectively after the year end at the point the accounts are in draft for a husband and wife partnership.
My previous employer, a firm of Chartered Accountants, had around 2,000 partnerships consisiting mainly of husband and wife corner shops in Birmingham. There were never any partnership agreements in place. After the end of the year profits were split in a manner which resulted in the lowest joint tax bill.
What was the profit sharing ratio in these cases? It was informally such split as the accountant would determine, after the year end, bearing in mind the spare personal tax allowances available to each of the spouses.
There was never any piece of paper to prove what the partnership agreement was. The clients would merely assume the profits would be split by the accountant in the manner which would result in the lowest tax bill. (In fact, I would guess many of these clients would probably have no concept of what a profit-sharing agreement was, their sole concern being their beloved accountant producing teeny-weeny tax bills as if by some miraculous sleight of hand).
Also note HMRC guidance which has some bearing on this at https://www.gov.uk/hmrc-internal-manuals/partnership-manual/pm132400
It would be interesting to learn what others do with their husband and wife partnerships.
And how on earth could HMRC dispute the apportionment each year if there is no piece of paper (Partnership Deed) to say otherwise? Partnership "Pillow Talk" agreement, perhaps?