Today is June 28, 2010 and there are only three more days left in pre-HST Ontario/BC. Those in the service industry (where files are maintained for clients) should bill for services rendered before July 1, 2010. Services rendered before July 1, 2010 are not subject to harmonized sales tax ("HST"). In addition, many services are not subject to Ontario retail sales tax ("ORST") - only "taxable services" as defined in the Retail Sales Tax Act (Ontario) are subject to ORST in Ontario.
I offer this advice to help not confuse an auditor - close any dormant files on Monday-Wednesday (June 28-30, 2010) (pre-HST period). Send those files to records (and you will not have to pay HST on the service fee of the moving company if the service is performed before July 1). Hire a temporary worker to provide assistance in the pre-HST period and save the HST. Both GST and HST are payable of the services provided by temporary employees services. If your employee (that is, he or she is on your payroll and is not a third party service provider or employed by a third party service provider) provides the assistance in closing the files in the computerized system and putting the files in boxes, then his/her employment related services are not subject to wither GST/HST.
You will both clean your office and save the HST at the same time. More importantly, you will have documentation to show that the files were closed prior to HST. You will have additional proof to give an auditor that you took steps to make a clear division for the purposes of the application of the HST transition rules. The easier you make it for the auditor, the easier you make it for yourself.
In addition, if that client comes back and needs more work performed by you post-HST, you can open a new file, gather the new information for your HST decision tree and start fresh (and start charging HST where applicable).