You must have sound substantial economic reason in order to allocate Profit & Loss percentages differently from your ownership percentage. IRS will not allow you to arbitrarily allocate income or deduction without economic reasons.
Here's an article on partnership allocations. Coownership of rental properties follows similar rules.
https://www.thetaxadviser.com/issues/2020/aug/partnership-allocations-lacking-substantial-economic-e...
In Holdner, T.C. Memo. 2010-175, the Tax Court found that deduction allocations between a father and son farming partnership were not in line with the partners' interests in the partnership. The court proceeded to analyze each of the four factors above and largely concluded that there was "no credible evidence" for the special allocations. "[I]n the absence of substantial proof rebutting the presumption of equality, [taxpayers] had equal interests in partnership income, expenses, and other partnership items." The court presumed that the father and son each owned 50% of the farming partnership, and the taxpayers did not provide sufficient evidence to refute that presumption. As it was determined that the father and son each had a 50% interest in the partnership, the IRS's assessment of substantial-underpayment and accuracy-related penalties was upheld.
