If your spouse is self-employed or owns a business, it can be harder to determine his or her actual income. If your spouse has business or professional partners, they can be a good source of information. You may have met them socially, or had an opportunity to meet the husband or wife of a partner and engaged in friendly conversation. Stay alert. One of these individuals may state important facts, or might provide useful information if you ask. For safety, speak to your lawyer first before initiating any contact.