In general, what documents does the corporation have to retain?

You must keep accounting records (software, transaction log), invoices, bookkeeping vouchers, bank statements, financial statements, copies of income tax returns, notices of assessment and other key documents. In other words, any document that could potentially be evidence in the event of a tax audit from the authorities.

Moreover, if you are working with non-incorporated subcontractors that do not have GST and QST numbers, make sure you have their name, address, invoices and social insurance number (SIN) for an eventual tax audit.

You must think about what a judge would do in such a situation. So make sure to always track your transactions.

To sum up, you must keep every document and record in order to prove your declarations. Keep in mind that problems can occur if you cannot show an official proof or explanation.