There is no difference between a change in partnership interest and taking on a new partner. Either case causes a change in the ownership allocation.
Example: 2 partners 50/50 take on a new partner. There is no longer a 50/50 ownership. The allocation and ownership percentages have changed to what ever this new 3rd partner acquired.
In another example, you can have a 50/50 ownership with A and B. If C buys out B, then you still have a 50/50 ownership, however, there has once again been a change in ownership and requires specific allocation as noted in my original reply.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
