- Sep 18, 2025
- 7 min read
How to Reverse Calculate Sales Tax in British Columbia (BC): A Step-by-Step Guide
If you receive a payment or invoice that already includes GST and PST, you may need to determine the base (pre-tax) amount and separate the tax components. This is called reverse calculating sales tax (or gross-to-net breakdown). In British Columbia, where 5% GST and 7% PST generally apply, the process involves a clear formula and awareness of exceptions. †
👉 Want to get the breakdown instantly? Try our Reverse Sales Tax Calculator for BC — just input the tax-inclusive total, and it will output the base, GST, and PST for you.
1. BC’s Sales Tax Structure: GST + PST
British Columbia uses a dual tax system: 5% federal GST and 7% provincial PST for most taxable goods and services. The PST rate is confirmed in the BC government’s Small Business Guide to PST (updated March 2025). †
Importantly, PST is applied to the pre-GST price (i.e., you don’t calculate PST on top of GST). The guide explains you “charge PST on the price … before adding the federal GST.” †
2. Why Reverse Calculate?
Reverse calculation is invaluable when:
- You receive a tax-inclusive total but need the base and separate taxes for accounting or reporting.
- You want to validate if tax was over-charged or under-charged.
- You’re reconciling receipts, preparing remittances, or doing bookkeeping.
3. The Reverse Tax Formula & Examples
Let:
Ttotal = total amount received (tax inclusive)
B = base amount (pre-tax)
GST rate = 0.05
PST rate = 0.07
Because PST is charged on the base price only, the formula is:
Total = Base × (1 + GST + PST)
Ttotal = B × 1.12
To isolate the base:
B = Ttotal ÷ 1.12
Then calculate:
GST = B × 0.05
PST = B × 0.07
Example: Suppose the total received is $224.00. Then:
Base = 224.00 ÷ 1.12 = $200.00
GST = 200.00 × 0.05 = $10.00
PST = 200.00 × 0.07 = $14.00
Sum check: 200 + 10 + 14 = 224 ✅
Prefer not to do this manually? Try our BC Reverse Sales Tax Calculator — enter a total and get the breakdown immediately.
4. Rounding & Exceptions
Rounding: You may see small rounding differences (± $0.01). Good calculators adjust one component slightly to ensure everything adds up.
Exceptions:
- PST is not charged on certain goods (e.g., basic groceries, medical equipment).
- Used zero-emission vehicles lost PST exemption as of May 1, 2025. †
- Accommodation may include an MRDT (Municipal & Regional District Tax) - handle that separately. †
5. Final Thoughts
Reverse sales tax calculations are straightforward once you understand the logic. But in practice, taxes, exemptions, and rounding rules make it easy to miscalculate.
Use the tool, not a spreadsheet: Try our BC Reverse Sales Tax Calculator - accurate, updated, and time-saving.
Sources
- Small Business Guide to PST (Province of British Columbia, March 2025) — gov.bc.ca
- 2025 British Columbia Budget — PST changes (used ZEV exemption ends May 1, 2025) — PwC Canada
- PST Publications & Bulletins — gov.bc.ca
- How to Know Which Taxes You Need to Collect — SmallBusinessBC.ca