In general, you can change profits allocations for a year up to the due date of that year's partnership return, not including extensions. So March 15 for a calendar-year partnership. So a change after year-end can be kosher, up to a certain point, and assuming it's permitted by your partnership agreement.
Whether the profits allocations will be effective is another issue. Your partnership will either comply with a SEE safe harbor or PIP. Most recent partnership agreements don't comply with SEE; an easy but not conclusive check is to look at the liquidation provision in the partnership agreement. If liquidation is in accordance with positive capital accounts, then you might be in SEE. If not, you're probably in PIP.
If you're in PIP, then the question is whether the new profits allocations will be respected. If you're balancing income allocations among partners because they weren't in alignment with the business deal, then that may work. If the partners involved both hold through retirement accounts, then any tax gaming is pretty attenuated. You really want to make sure that the tax allocations track real shifts in the partnership's economics--who gets what in terms of distributions. Your accountant, or the lawyer who did the partnership agreement, may be able to help in that respect.
