If you discover an error on a GST/HST return you already filed, request an adjustment; do not file another return for the same period. CRA accepts eligible adjustments through a business account or by signed letter. Keep your original return, calculations and supporting documents so you can explain the change. CRA: change a filed return
First identify what needs changing
Find the RT account and reporting-period dates on the original return. Reconcile the relevant sales, GST/HST collected or collectible, eligible input tax credits (ITCs), and other entries against invoices and records. Work out the correct total for each affected line; for example, if line 101 was $5,000 but should have been $6,000, the corrected total is $6,000. A change may affect the net tax, interest or refund.
A forgotten eligible ITC may sometimes be claimed on a later return within its applicable time limit, so an adjustment is not always needed solely to claim that credit. For most registrants, CRA measures the four-year limit through the due date of the last return period ending within four years of the original period; a two-year limit applies to certain registrants. Check the business-use and documentation conditions and do not claim the same ITC twice. CRA: ITCs and time limits
Request an adjustment online
- Sign in to your CRA account and access My Business Account or Represent a Client.
- Choose GST/HST and the correct RT account, then select Adjust a return.
- Choose the reporting period from the list of periods eligible for electronic adjustment and make the changes using the corrected figures.
- Review and submit the request. Keep the confirmation and a copy of your supporting calculations, then monitor the account for CRA’s response. CRA: change a return
Request an adjustment by mail
If electronic adjustment is unavailable or you choose the written route, send a letter to your tax centre, signed by the owner or an authorized representative. Include the business number and RT extension, the reporting period, corrected amounts for each affected line, and the name and telephone number of a contact. Keep a copy of the letter and the underlying records. CRA: adjustment information
Missed return or disputed assessment?
If you never filed the return, file the missing period instead of requesting an adjustment. If you disagree with an assessment or reassessment, an adjustment request is different from a formal objection. The GST/HST objection deadline is generally 90 days after the notice was sent; asking for an adjustment does not replace that deadline. A personal income-tax T1 return has separate correction and objection rules. CRA: GST/HST objections
Do not assume an adjustment has the same processing time as an original return or that a refund is guaranteed. Check your account, and contact CRA if you need information about an outstanding request. For accounts administered by Revenu Québec, use its applicable process. CRA: after filing