"would it be shown the K1 as a retirement plan contribution, and deducted by the partnership as an expense?"
It should be shown in box 13 with code R but is not deducted by the partnership as an expense. It gets deducted on your individual tax return. In TurboTax Business you simply enter the total of the additions to the plan made on the partner's behalf and the number is placed in box 13 with code R.
The amount shown in box 13 of the Schedule K-1 (Form 1065) with code R should be the total of the employee contributions and employer contributions. When this is entered into TurboTax for your individual tax return, TurboTax will ask you for the breakdown.
