Alan needs to pay a total of $48 to Robin, but he only has $36. This means he needs to overdraw his account by:
\[ 48 - 36 = 12 \]
So, Alan overdraws his account by $12 to make the payment. Assuming his account balance was initially $0, after the payment and including the overdraft, his new account balance will be:
\[ 0 - 12 = -12 \]
Therefore, after paying Robin, Alan's account balance will be -$12.