There could be a few different reasons why the time may have come for you to close your GST account with the CRA.
To close your account you need to complete form RC145 Request to Close Business Number Accounts and send it to your tax services office. You must also make sure that you file any outstanding GST returns for the period up to the date the account is closed and pay any remittances due. If you are closing the business you are assumed to be disposing of the assets of the business and that you have collected GST on these sales. You will need to determine the fair market value of these assets and report this on the return.
If you do not close the account the CRA will assume that you are still in business and will expect you to file returns. If your business is closed or inactive you can file nil returns until your business starts up again, but if you continue to file nil returns for several years the CRA may contact you to ask if you want to close the account. If you stop filing returns and don't close the account the CRA will require you to file for the missing dates and if you do not respond you can expect to receive a phone call or visit from from a CRA officer. If your business is still open and you are not filing returns you will be prosecuted under the Excise Tax Act and you will be liable for penalties and interest.
From an article by Susan Ward
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