Depending on the size of your firm and the number of different departments involved, you may want to appoint a single co-ordinator to act as the spokesperson. Set up a pre-audit meeting with Customs to break the ice and to establish the objectives and parameters. The corporate team should exchange names and telephone numbers with the audit team. Customs accept voluntary disclosures without penalty up to the date of the official commencement of the audit. This audit should be handled no differently than an income tax or sales tax audit.
Good communication is critical.
Deal with any questions that arise quickly and efficiently. Set out realistic time frames and stick to them. Make sure any agreements or other significant issues are confirmed in writing. Don't commit to anything you can't deliver. At the end of the audit process, assuming your firm has not been as compliant as Revenue Canada would have liked, there will be some discussion and eventual agreement about the minimum requirements respecting proper maintenance of books and records.