Reverse HST Calculator Canada

Reverse tax calculation (sometimes called tax extraction or backing out tax) is the algebraic process of separating the original pre-tax price from the tax amount when you only know the grand total.

To do this manually, convert the provincial sales tax rate to a decimal, add 1, and divide the total by that amount:

For example, if you purchased an item in Nova Scotia for $114.00 CAD (where the HST is 14%):

For corporate accountants and small business bookkeepers in British Columbia, Saskatchewan, and Manitoba, reverse tax calculation is critical. Because these provinces operate dual-tax systems (federal GST + provincial PST), you cannot simply apply a single tax credit.

The Canada Revenue Agency allows you to reclaim the 5% federal GST portion as an Input Tax Credit (ITC). However, provincial retail sales taxes (PST/RST) are generally not reclaimable as ITCs. Under provincial tax codes, PST paid on commercial supplies is treated as a standard operating business expense. Failing to separate the two leads to inaccurate tax returns, potentially prompting CRA audits and tax penalties.

The CRA enforces strict guidelines for backing out taxes. To legally claim an ITC on your GST/HST return, the business must possess written proof of transaction containing:

• The vendor's registered Business Number (GST/HST registry ID).
• The date of the transaction and description of goods/services.
• A clear breakdown of the sales taxes paid (GST, HST, or PST).

If the invoice lists only a tax-inclusive total with a note saying 'taxes included', the CRA requires you to reverse-calculate the tax based on the official rate of the customer's province. Our reverse GST calculator simplifies this bookkeeping process.