For the first 4 of the past 6 months, I've tried disclosing early (first or second phone call), half-way through, or near the job offer phase. Every single time, without fail, they email back (not even a phone call) with either a generic or very brief message retracting their offer or declining to proceed with the interview process. Smaller companies will simply stop returning my calls and emails, and completely cut off contact regardless of when I tell them. I only started waiting until the background check until I disclose for the past 2 months because I'm getting very nervous about not actually getting a job.