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I am not familiar with the Purchase Transaction Detail report specifically by that name, can you tell me how you are getting that report to run (which menu options eg. from the Sage 50 Home Screen, Reports, Payables, Vendor Purchases, Detail)?  Is it Reports, Transaction Detail, Purchases?

Based on the rest of your message, it might be that your sales taxes are not set up properly with the HST as Refundable.

From the Home Screen if you select Setup, Settings, Company, Sales Taxes, Tax Codes and double-click your HST tax code, do you see under the "Is Refundable" column Yes or No?

If No, then it is not set up properly.

You will have to change this from No to Yes to correct the entries for the future.

But this will not correct entries already posted.  You will have to remove the original entry and post the entry over again if you wish the HST to be allocated to the liability account properly on each purchase entry.  If any of your entries are already paid, you might wish to use the following idea rather than create several credit memos.

You can post a general journal entry to update the HST Paid Liability account and remove the extra tax from the expense/other accounts already posted to as well if you are dealing with a lot of entries.  It might be easier to do the math on all the entries and post the adjusting entry.

I have a similar problem.  However, the HST is not showing on the purchase report, but it does come up when I run the quarterly tax report for remittances.  However, when I run an income statement, the amount for purchases includes the HST.  Any ideas?  The sales revenue on the income report does not include the HST and I have no idea why it is doing that.