no. it is not a partnership expense for tax purposes. however, it is usually treated as a book expense.
example:
net income before retirement plan contributions 300 schedule K line 1
self-employment income schedule K line 14a 300
retirement plan contribution line 13d code R 20
analysis of net income 280
M-1 line 1 net income per books 280 and line 9 and M-2 line 3 (assuming retirement plan contributions are charged against book income and not charged to the partnership's capital accounts directly
