Discount Stacking Calculator: True COGS After Tax and Rebates

Calculate true retail arbitrage buy cost after sales, coupons, sales tax, cashback, card rewards, rebates, quantity, and resale fees. Use the effective COGS and decision panel before buying.

Quick presets:

Original Price

Sale Discount

Coupon Type

Coupon Value

Sales Tax Paid

Cashback Basis

Cashback %

Credit Card Rewards %

Rebate / Store Credit

# of Identical Items

Expected Resale Price

Resale Platform

Fee presets use the reviewed U.S. calculator policy (2026-10-01). Tax and rebate notes were checked 2026-08-06; verify store and portal terms before relying on delayed credits.

Your Effective Cost

$65.10

After sales tax, discounts, rewards, and rebates

34.9% OFF

Saved $34.90

Savings Breakdown

Original Price$100.00

Sale (20% off)-$20.00

Coupon-$10.00

Discounted Subtotal

$70.00

Checkout Total$70.00

Cashback (5% on subtotal)+$3.50

CC Rewards (2%)+$1.40

Effective Cost

$65.10

Decision

Use effective cost as COGS

Copy the effective cost into your ROI or fee calculator before you buy.

Compound Savings Formula

Step 1 - Sale

After Sale = $100.00 x (1 - 20%) = $80.00

Step 2 - Coupon ($10 off)

After Coupon = $80.00 - $10.00 = $70.00 (you pay)

Step 3 - Cashback & CC Rewards

Cashback = $70.00 x 5% = +$3.50

CC Rewards = $70.00 x 2% = +$1.40

Result

Checkout total = $70.00 + $0.00 = $70.00

Confirmed credits = $3.50 + $1.40 + $0.00 = $4.90

Effective Cost = $70.00 - $4.90 = $65.10

Total Savings = $100.00 - $65.10 = $34.90 (34.9% off)

Sourcing cue: Compare ROI on effective cost, but keep checkout total, tax paid, and delayed reward credits separately in your records.

How to Use the Discount Stacking Calculator

Use this tool when a clearance or coupon stack looks profitable but the real buy cost is spread across checkout cash, sales tax, delayed cashback, card rewards, and rebates. The calculator separates those pieces so you can use an honest COGS number in your resale math.

Start with the shelf price. Enter the original price before sale markdowns and coupons.
Add checkout costs. Include sale percent, coupon amount, and any sales tax actually paid.
Add delayed credits carefully. Choose whether cashback is based on pre-tax subtotal or checkout total, then enter card rewards and rebates separately.
Run a resale check. Enter the conservative resale comp and expected platform fee before treating the stack as a buy.

Checkout Total vs Effective COGS

Checkout Total

This is the cash you pay at the register after sale discounts, coupons, and sales tax. It matters for card limits, cash flow, receipts, and returns.

Effective COGS

This subtracts confirmed cashback, card rewards, rebates, and store credits from checkout total. Use it only when those credits are trackable and tied to the purchase.

Delayed Credit Risk

Portal cashback and rebates can fail, cap, exclude coupons, or arrive later. The decision panel warns when the estimated margin relies too heavily on delayed tracking.

Resale Fee Check

A stack is not a buy unless a conservative sold comp clears the effective COGS after platform fees and realistic condition assumptions.

Decision Guardrails

Signal	Why It Matters	Next Action
Credits exceed checkout	A coupon, rebate, or reward may be entered incorrectly or may not stack.	Verify terms before buying.
Negative resale profit	The sold comp does not cover fee-adjusted effective cost.	Skip, negotiate lower, or find a stronger comp.
High delayed-credit share	Margin depends on later approvals instead of cash price.	Save screenshots, receipts, activation proof, and tracking IDs.

Source and Recordkeeping Notes

Marketplace records may not net everything out.

IRS 1099-K guidance says gross payment reports are not adjusted for fees, refunds, shipping, discounts, or other offsets. Keep your sourcing math and payout records together.

Rebates and rewards need evidence.

Treat cashback, card points, and rebates as assumptions until tracked. Terms can exclude coupon codes, gift cards, categories, taxes, shipping, or marketplace purchases.

Checked 2026-08-06.

Fee presets come from the shared calculator policy review, and tax/reward notes were checked for this free-tool batch. Recheck store and portal terms before high-volume sourcing.

Frequently Asked Questions

What is effective cost in discount stacking?

Effective cost is checkout total minus confirmed cashback, card rewards, rebates, and store credits. It is the number to test in a profit calculator when those credits are reliable.

Should sales tax be included?

Yes when you paid it at checkout. If a valid resale certificate removes tax on qualifying inventory, set the sales tax field to zero and keep the certificate proof with the receipt.

Can I add cashback percentages together?

No. Discounts happen in sequence, and cashback may apply to a different basis than the coupon subtotal. Use the basis selector and keep each credit separate.