Imagine you own a small company and you form an interest group to lobby your elected representatives. which category of interest group organization would yours fall under?

non membership organization

Explanation:

Lobbying is the activity of influencing or persuading the government or the federal legislatures in decision making or policy making.

Non membership organization falls under those category of organization which have limited opportunities to lobby or do advocacy under the section  501(c)(3). Too much of lobbying activities might risk the organization to loose the tax exemption status.

Hence the answer is -- "non membership organization"