You may import accrual-based accounts and convert them to cash basis. Click here "Why Accrual import?" 

Adjust in prior year and adjust current year  accounts receivable &/or payable,  via "Income" > "Business" in PTR form,

Simply press the button and set to "YES". To expose the section to report the GST component. It is important to recognise the GST associated with your accounts receivable & payable values since the GST component should not be part of the reconciling adjustment.

Related Article:

Cash vs Accrual Reporting in Tax Forms

GST Reconciliation - Cash GST reporting and Accrual accounting