Quoting ChaceAndMama:" I live in British Columbia, and my ex (father of my son) JUST started working... My son is 5 months old ... [snip!] ... an answer for what I need. Also, will the support pay be backed up? Will he have to pay for the last 5 months in bulk? Thanks!"
You should definitely contact them and let them know he's began working. They will then tell him how much he needs to start paying and most likely set up a payment plan for the backpay he owes. It shouldnt have to be in bulk but like maybe an extra $50 on top of what he regularly owes until all the last 5 months has been paid off ya know?
The sooner you call the better. If he ends up not paying on his own then they should be able to garnish his wages and have money sent directly to you from his paychecks.