Every car lease payment is deterministic. Given the net capitalized cost, residual value, money factor, and your state's tax structure, the math produces exactly one number — there is no wiggle room and no guessing. That's also why it's so easy to verify.
This post walks through three real deals against actual dealer signing documents — actual VINs, actual line items, actual numbers: a 2026 Mercedes-Benz GLC 300 in Louisiana, a 2026 Kia EV9 Wind AWD in Oregon, and a 2026 Lexus TX 350 Premium AWD in Georgia. Three states. Three lenders. Three different tax structures.
I built QuoteDefender because this math is technically disclosed on every dealer document — the MF is on page 3, the fee breakdown is itemized — but it's not in a format where you can act on it at signing. These three deals are the verification record.
Louisiana
2026 Mercedes-Benz GLC 300
MF ~0.00395 · 36 mo · 10k mi
Score: 41/100
Oregon
2026 Kia EV9 Wind AWD
MF 0.00197 · 24 mo · 10k mi
At buy rate — no markup
Georgia
2026 Lexus TX 350 Premium AWD
MF 0.00325 · 36 mo · 12k mi
Score: 32/100
The Core Formula
Every lease payment is two numbers added together:
// The entire lease payment engine
Monthly = Depreciation + Rent Charge
Depreciation = (NCC − RV) / Term
Rent Charge = (NCC + RV) × Money Factor
// Where:
NCC = Net Capitalized Cost (what you're financing)
RV = Residual Value (car's worth at lease end)
MF = Money Factor (APR ÷ 2400)
Every number on a dealer quote reverse-engineers back through this formula. If the inputs are right, the output is exact.
The numbers verify to the cent
Lexus TX 350 — Georgia
| Line Item | QD Output | Independent Calculation | Match |
|---|---|---|---|
| Amount Leased (NCC) | $69,736.43 | $69,736.43 | ✓ |
| Value Loss / mo | $781.85 | $781.85 | ✓ |
| Interest / mo | $361.81 | $361.81 | ✓ |
| Rate markup savings | $3,206 | $3,206 | ✓ |
Kia EV9 — Oregon
| Line Item | QD Output | Independent Calculation | Match |
|---|---|---|---|
| NCC (Balance) | $51,729.70 | $51,729.70 | ✓ |
| Payment at $0 drive-off | $489.15 | $489.15 | ✓ |
| Payment at $2,500 drive-off | $373.88 | $373.88 | ✓ |
GLC 300 — Louisiana
| Line Item | QD Output | Verification | Match |
|---|---|---|---|
| APR equivalent | 9.5% | Back-calculated from dealer NCC | ✓ |
| Rate markup savings | $3,961 | Verified against MBFS buy rate | ✓ |
Two of three dealers marked up the money factor — one nearly doubled it
The biggest lever in any lease deal is the Money Factor. Captive lenders — Lexus Financial Services, Mercedes-Benz Financial Services, Kia Motor Finance — publish a "buy rate," the floor MF they'll approve for a qualified buyer. Dealers can mark it up and keep the spread as profit. It's functionally identical to a loan origination fee, just expressed differently.
// MF markup cost formula
$/mo savings = (NCC + RV) × (Dealer_MF − Buy_Rate_MF)
| Car | Buy Rate MF | Dealer MF | Markup | $/mo extra | Total cost |
|---|---|---|---|---|---|
| Lexus TX 350 (GA) | 0.00245 | 0.00325 | +0.00080 | $87/mo | $3,144 |
| GLC 300 (LA) | 0.00198 | ~0.00395 | +0.00197 | ~$110/mo | ~$3,960 |
| Kia EV9 (OR) | 0.00197 | 0.00197 | $0 | $0 | $0 |
The EV9 deal was at buy rate — the dealer didn't mark up the MF at all. QD's score reflects this. The GLC 300 had the worst markup: the dealer roughly doubled the buy rate. In each case, QD's savings figure matched independent calculation.
State tax structures
Different states tax leases differently, and it directly changes how NCC is built.
Georgia charges 7% on total depreciation (NCC − RV), capitalized into the NCC at signing. It's not a monthly stream — it compounds into the financed amount.
GA Tax = 7% × ($69,736.43 − $41,589.76)
GA Tax = 7% × $28,146.67 = $1,970.27
Dealer document: $1,970.27 ✓
The CCR feedback effect: When a Georgia buyer puts cash down, the taxable depreciation base shrinks, which reduces the GA tax, which further reduces NCC. Each $1 of customer cash reduces the NCC by ~$1.077 — not $1.00 — because of this iteration. QD's NCC figures for different cash-down scenarios account for this correctly.
Louisiana applies ~9.95% to each monthly payment. QD's "Total Cost" figure correctly included stream tax across all 36 payments — not as an upfront lump sum.
Oregon has no general vehicle sales tax, but does have a Corporate Activity Tax that dealers pass through as a separate line item. QD correctly separated this from junk fees and DMV fees rather than collapsing them.
Fee classification
QD sorts every fee into three buckets: government (fixed/unavoidable), negotiable (optional/dealer-chosen), and lender (partially negotiable).
Lexus TX 350 — Georgia
| Fee | Amount | QD Classification | Correct? |
|---|---|---|---|
| Window Tint | $499 | Junk — negotiable | ✓ |
| Dealer Service Charge | $899 | Negotiable ($300 over typical) | ✓ |
| Acquisition Fee | $895 | $195 markup over $700 base | ✓ |
| DMV / Registration | $244.50 | Government fee | ✓ |
| GA Lease Tax | $1,970.27 | Government / capitalized | ✓ |
| First Payment (LFS program) | $1,143.66 | Capitalized into NCC | ✓ |
The "First Payment Waived" mechanic
The dealer document showed Amount Financed = $69,736.43, but itemized fees summed to only $68,592.77. The $1,143.66 gap is the first monthly payment capitalized into the NCC under Lexus Financial's flat-fee program. The customer doesn't pay it at signing — it's deferred across all 36 payments. It's not a free payment; it's a capitalized one.
GLC 300 — Louisiana
Doc fee: $436 vs. Louisiana's CPI-indexed statutory cap of $425 — $11 over the legal limit.
Kia EV9 — Oregon
Deal came through an Edmunds Price Promise dealer: $0 doc fee, $0 add-ons, $0 MF markup. When a dealer doesn't mark anything up, there's nothing to flag. QD's score improved accordingly.
Deal scores: 32, 41, and 82 — and why
Lexus TX 350 (GA)
32
/ 100
MF +33% above buy rate
$1,398 in negotiable fees
GLC 300 (LA)
41
/ 100
MF ~100% above buy rate
Doc fee over legal cap
Kia EV9 (OR)
82
/ 100
At buy rate
$0 doc fee, $0 add-ons
A 32/100 deal where the dealer marked up the MF by a third and added nearly $1,400 in negotiable fees is exactly what that score should say. The GLC 300 scored slightly higher only because its selling price was competitive — the rate markup was far worse.
$4,005 in savings on the Lexus — here's exactly where it comes from
QD's potential savings figure on the Lexus TX 350 was $4,005:
Rate markup savings (MF 0.00325 → 0.00245, 36 mo): $3,206
Doc fee over typical ($899 − $599 standard): $300
Junk fee — window tint: $499
Total: $4,005 ← QD's stated figure ✓
This is conservative — it doesn't claim you'll capture all of it, just that it's on the table. The rate markup alone ($3,206) is the non-negotiable win if you get Lexus Financial to honor the buy rate. The fee savings require pushing back at the dealer.
The negotiation math follows directly:
// Cleaned NCC at $2k cash
Dealer NCC at $2k cash: $67,583
- Window Tint ($499 ÷ 0.93 tax adj): −537
- DSC ($899 ÷ 0.93 tax adj): −967
= Cleaned NCC: $66,079
Payment at buy rate MF 0.00245: ~$1,008/mo ✓
The negotiation script is simple: "I want MF 0.00245 — that's Lexus Financial's published buy rate. And I'd like to remove the window tint and dealer service charge from the capitalized cost."
What Dealer Paperwork Obscures
None of this is secret. The buy rate is public. The fee breakdown is on the contract. What's missing is a format that makes the numbers actionable.
- The MF on your quote is buried on page 3 in a box labeled "Lease Rate" as a decimal like
.00325— with no reference to what the buy rate is or what the markup costs you. - The "First Payment Waived" program sounds like a dealer concession. It's a deferral capitalized into the principal — you finance it across all 36 payments at the lease rate.
- The GA lease tax looks like a fixed government charge (it is), but its exact amount depends on your deal structure because the taxable base changes with cash down.
- Louisiana's stream tax applies to every monthly payment; Georgia's is collected once at signing. The same ~7–8% rate produces materially different total costs depending on which structure applies — and the dealer's quote won't tell you which you're in.
Summary
Buy rate MF verified for Lexus Financial, MBFS, and Kia Motor Finance
State tax structures: GA capitalized TAVT, LA stream tax, OR CAT pass-through — all correct
Fee classifications matched itemized dealer documents
Georgia CCR tax feedback effect computed correctly
Savings estimates conservative and independently confirmed
Negotiation targets mathematically derivable from the inputs
QuoteDefender's value isn't that it tells you something the dealer is hiding. It's that it takes information the dealer is technically disclosing — buried in a wall of line items — and puts it in a format where you can actually act on it.
The buy rate is public information. The fee breakdown is on the contract. QD just does the math.
Want to run your own quote through the same analysis? — upload your dealer quote and get NCC, MF markup, fee breakdown, and savings estimate.
