Hi does anyone know if discover has negative balances period? And if they do does that extend available credit? For example I want to spend 20k with a 10k CL so can I send in a check for 10k have it post to a -10k balance and go swipe 20k without having to go home and wait for 10k to post and go again? I know citi, chase and Amex do this. Barclays does not.