P
Glossary
Partial Refund
A partial refund returns part of a payment to the customer while the rest of the original transaction stands. The seller derives the amount from unused time, unused quantity, or one disputed charge, then returns the tax belonging to that amount, not the tax on the whole sale.
Key Takeaways
The refunded figure comes from a ratio, not a judgment call. Most subscription refunds use unused days over days in the period.
Sales tax comes back in proportion to the amount refunded. New York's tax department ruled in TSB-A-09(29)S that a customer gets tax back only as far as the original transaction is undone.
On a $900 monthly charge taxed at 8%, refunding 18 unused days of 30 returns $540.00 plus $43.20 of tax, and the seller still remits $28.80 on the $360 it kept.
Card processing fees from the original payment don't come back, so a 60% refund costs more than 60%.
Refunds return to the original payment method only, so a customer whose card expired since the charge lands in a support queue.
How do you calculate a partial refund?
You calculate a partial refund by fixing the share of the original charge the customer no longer owes, then applying that share to the charge and its tax separately. The ratio and its base decide everything else.
The order that keeps the arithmetic honest:
Pick the base. The refund attaches to a specific invoice line item, not the invoice total, since lines differ in rate and proration rule.
Derive the ratio. Time-based charges use unused days over days in the billing period, quantity-based charges use units returned over units billed.
Apply the ratio to the pre-tax amount and round once, at the end.
Recalculate tax on the refunded amount at the rate in force on the original sale date.
Check the running total. Refunds against one payment can't exceed what the customer paid.
A mid-cycle cancellation on a $900 monthly plan, 8% sales tax, 30-day period, effective at the end of day 12:
Line | Amount |
|---|---|
Plan charge for the period | $900.00 |
Sales tax at 8% | $72.00 |
Original charge | $972.00 |
Unused days over days in period | 18 / 30 |
Refunded plan amount (900 x 18/30) | $540.00 |
Tax on the refunded amount (540 x 0.08) | $43.20 |
Total refund | $583.20 |
Tax on the retained $360, still remitted | $28.80 |
The two tax figures foot back to the $72 collected, and the customer still pays for the 12 days used.
What happens to tax on a partial refund?
Tax comes back in proportion to the refunded amount, and the tax on what you keep stays with the tax authority. Returning the full tax overstates your credit and surfaces in an audit.
New York's Department of Taxation and Finance settled this in advisory opinion TSB-A-09(29)S, issued 15 July 2009. Sales tax is a transaction tax, so it unwinds only as far as the sale does. The opinion works a $100 item taxed at 8% and refunded at 50%: $50 goes back plus $4 of tax, and the other $4 stays remitted and uncreditable.
What that means on a taxed sale:
The rate is the one in force on the original sale date. A change since then doesn't touch a correction to an earlier sale.
Amounts you hold back, restocking and early-termination fees among them, are receipts in their own right and may carry tax.
You reclaim the tax you returned only once the customer has it, so the credit follows the payment.
Cross-border sales follow the buyer's jurisdiction, as the original charge did under sales tax for SaaS.
Where do partial refunds fail?
Partial refunds fail at the seams between the billing system, the gateway, and the ledger, almost never at the arithmetic. The refund calculates cleanly and something downstream disagrees.
The breaks that recur:
Fee asymmetry. Stripe states that its processing fees from the original transaction aren't returned, so a 60% refund gives up 60% of revenue and keeps 100% of the cost.
The cumulative cap. Several refunds can land on one charge, but their total can't exceed the original amount. Two teams crediting the same invoice find that out at the gateway.
Dead payment methods. Refunds go back to the original card only. When that card is closed or expired, the refund fails and the money returns to you weeks later.
The missing document. A gateway refund is a payment record, not a tax document. Without the matching credit note your declared tax stays overstated, which is what credit note vs refund covers.
Reconciliation gaps. A refund issued in the gateway but never posted to the invoice leaves an unexplained line in payment reconciliation.
Related terms
A partial refund touches all of these, some in the charge it corrects and some in the paperwork behind it.
Billing period supplies the day count proration ratios divide by.
Invoice line item is the row a partial refund attaches to, with its own rate and tax treatment.
Credit note vs refund decides whether the correction moves cash at all.
Credit memo records the reduction against the original invoice.
Sales tax for SaaS sets the rate and jurisdiction the refunded tax must match.
Payment reconciliation is where an unposted refund shows up as a stray bank line.
FAQ
How long does a partial refund take to reach the customer?
Card refunds typically appear 5 to 10 business days after the seller issues them, depending on the issuing bank. A refund raised soon after the charge may process as a reversal instead, which drops the charge off the statement with no separate credit.
Can you issue more than one partial refund on the same payment?
Yes, as long as the combined total stays at or below the original charge. Gateways enforce that ceiling and reject the request that crosses it.
What's a prorated refund?
A prorated refund is a partial refund whose ratio comes from time rather than quantity: unused days divided by days in the period. That's the standard treatment for a mid-cycle cancellation.
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