Incorporating your shop usually means the company's debts stay with the company. Source deductions are the big exception. The CPP, EI and income tax you withhold from a worker's pay aren't really your company's money — you're holding it in trust for the CRA. When that trust money isn't remitted, the people who run the company can be made to pay it personally.
That's director liability. If a corporation fails to remit the amounts it deducted, the CRA can assess the directors directly for the unremitted source deductions — plus interest and penalties. "The bureau was supposed to handle it" is not, on its own, a defence. The directors are expected to have exercised reasonable care to make sure the remittances actually went out.
The trap is that this risk is invisible right up until it isn't. A bureau sends a confirmation that payroll ran; that's not the same as a confirmation the remittance landed at the CRA. Months can pass before an assessment shows up, by which point it's a personal debt, not a line on a company statement you can dispute and move on from.
The defence is boring and effective: keep clean, dated records of every remittance and be able to confirm each one reached the CRA. That's exactly what Onest is built to give you — a traceable ledger where every deduction shows its formula and every remittance is confirmable, so the trust money is accounted for and you can prove it.