There is an entry in the Partnership K-1 input screen (Individual module), in the Line 20 section, for Portion of guaranteed payments received for use of capital and not subject to SE tax.

The F1 help for this input says: 

Enter the portion of the guaranteed payments included in box 4 that were received for the use of capital and are not subject to self-employment tax. This amount will be subject to net investment income tax (Form 8960).

Generally, guaranteed payments are not subject to net investment income tax. Guaranteed payments received for services are not subject to net investment income tax. Similarly, guaranteed payments that are subject to self-employment tax are not subject to net investment income tax.