I third that.
When I applied for Kay Jewelers, I noticed the online app said "Household Income," so that's what I put. Apparently there was a technical glitch when I submitted my app, and it didn't go through, so I called to see if they had an app pending for me and find out whether I should reapply or if they actually got it. Turned out they didn't get it, but the rep convinced me to just apply over the phone with her. When we got to the same question, she asked me my salary, not household income. Remembering what the online app said, I asked her, "Are you asking for my household income?" to which she replied, "No, just your salary."
Bottom line, approved for $1500, but I'm sure I could have gotten more if I had been able to use HHI instead.