AMBAC ASSURANCE CORPORATION NOTE GUARANTY INSURANCE POLICY

Exhibit 10.5

AMBAC ASSURANCE CORPORATION

NOTE GUARANTY INSURANCE POLICY

Policy No. AB1053BE

For consideration received, AMBAC ASSURANCE CORPORATION, a Wisconsin domiciled stock insurance corporation (“Ambac” or the “Insurer”), in consideration of the payment of the insurance premium payable with respect hereto, hereby unconditionally and irrevocably guarantees, subject only to (i) proper presentation of a Notice in accordance with the terms of this Note Guaranty Insurance Policy (together with each and every endorsement, if any, hereto, the “Policy”) and (ii) the terms of the

Policy, the payment to, or at the direction of, the Indenture Trustee, for the benefit of the Holders of the Insured Obligations, that portion of the Policy Claim Amounts which are Due for Payment but are unpaid by reason of Nonpayment.

1. Definitions.

Capitalized terms used herein and not otherwise defined shall have the meaning assigned to them in the Insurance Agreement or, if not defined therein, in the Sale and Servicing Agreement, or, if not defined therein, in the Indenture, without giving effect to any subsequent amendment or modification thereto unless such amendment or modification has been approved in writing by Ambac. For purposes of the Policy, the following terms shall have the following meanings:

“Affiliate” shall mean, with respect to any specified Person, any other Person controlling or controlled by or under common control with such specified Person. For the purposes of this definition, “control” when used with respect to any Person means the power to direct the management and policies of such Person, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise; and the terms “controlling” and “controlled” have meanings correlative to the foregoing.

“Bankruptcy Code” shall mean Title 11 of the United States Code.

“Basic Documents” shall mean the Sale and Servicing Agreement, the Certificate of Trust, the Trust Agreement, the Sale Agreement, the Insurance Agreement, the Indenture, the Spread Account Agreement and all other documents and certificates delivered in connection therewith.

“Business Day” shall mean a day other than (a) a Saturday or a Sunday, (b) a day on which the Insurer is closed or (c) a day on which banking institutions in New York City, Newport Beach, California, Wilmington, Delaware or in the city in which the corporate trust office of the Indenture Trustee under the Indenture or the Owner Trustee under the Trust Agreement is located are authorized or obligated by law or executive order to be closed.

“Class A Notes” shall mean, collectively, the Class A-1 Notes, the Class A-2 Notes and the Class A-3 Notes.

“Collection Account” shall mean the account designated as such, established and maintained pursuant to Section 5.1 of the Sale and Servicing Agreement.

“Distribution Date” shall mean, with respect to each Collection Period, the 15th day of the following calendar month, or, if such day is not a Business Day, the immediately following Business Day, commencing January 16, 2007.

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“Due for Payment” shall mean, with respect to any Policy Claim Amounts, such amount as is due and payable pursuant to the terms of the Indenture.

“Final Scheduled Distribution Date” shall mean, with respect to (i) the Class A-1 Notes, the December 17, 2007 Distribution Date, (ii) the Class A-2 Notes, the December 15, 2009 Distribution Date and (iii) the Class A-3 Notes, the August 15, 2012 Distribution Date.

“First Distribution Date” shall mean January 16, 2007.

“Holder” shall mean any registered owner of a Class A Note (other than a United Party).

“Indenture” shall mean that certain Indenture, dated as of December 1, 2006, by and between the Issuing Entity and the Indenture Trustee.

“Indenture Trustee” shall mean Deutsche Bank Trust Company Americas, not in its individual capacity but as trustee under the Indenture, and its successors and assigns in such capacity.

“Insurance Agreement” shall mean that certain Insurance and Indemnity Agreement, dated as of December 14, 2006, among the Insurer, the Issuing Entity, UACC, the Seller and the Indenture Trustee, in regard to the Class A Notes, as such agreement may be amended, modified or supplemented from time to time.

“Insured Payments” shall mean, (i) with respect to any Distribution Date, the aggregate amount actually paid by the Insurer to, or at the direction of, the Indenture Trustee in respect of the amounts set forth in clause (i) of the definition of Policy Claim Amounts for such Distribution Date and (ii) the aggregate amount of any Preference Amounts paid by the Insurer on any given Business Day.

“Insurer” shall mean Ambac, or any successor thereto, as issuer of this Policy.

“Interest Period” means with respect to any Distribution Date (i) for the Class A-1 Notes, from and including the prior Distribution Date (or in the case of the first Distribution Date, from and including the Closing Date) to, but excluding, the current Distribution Date, and (ii) with respect to the Class A-2 Notes and the Class A-3 Notes, from and including the 15th day of the preceding calendar month (or, in the case of the first Distribution Date, from and including the Closing Date) to , but excluding, the 15th day of the month of the current Distribution Date.

“Interest Rate” shall mean, with respect to (i) the Class A-1 Notes, 5.34% per annum, (ii) the Class A-2 Notes, 5.15% per annum and (iii) the Class A-3 Notes, 5.01% per annum (in the case of the Class A-1 Notes, computed on the basis of a 360-day year and the actual number of days in the related Interest Period and, in the case of the Class A-2 Notes and the Class A-3 Notes, computed on the basis of a 360-day year consisting of twelve 30-day months).

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“Issuing Entity” shall mean UPFC Auto Receivables Trust 2006-B, a Delaware statutory trust.

“Late Payment Rate” shall mean the lesser of (a) the greater of (i) the per annum rate of interest publicly announced from time to time by Citibank, N.A. as its prime or base lending rate (any change in such rate of interest to be effective on the date such change is announced by Citibank, N.A.), plus 2% per annum and (ii) the then applicable highest rate of interest on the Class A Notes and (b) the maximum rate permissible under applicable usury or similar laws limiting interest rates. The Late Payment Rate shall be computed on the basis of the actual number of days elapsed over a year of 360 days.

“Maximum Insured Amount” shall mean $250,000,000 in respect of principal, plus interest thereon calculated at the applicable Interest Rate for the Class A Notes.

“Nonpayment” shall mean, with respect to any Distribution Date, Policy Claim Amounts which are Due for Payment but have not been paid pursuant to the Indenture.

“Notice” shall mean the telephonic or telegraphic notice, promptly confirmed in writing by telecopy substantially in the form of Exhibit A or Exhibit B, as applicable, to this Policy, the original of which is subsequently delivered by registered or certified mail, from the Indenture Trustee specifying the amount of any Policy Claim Amount which shall be due and owing.

“Order” shall have the meaning given such term in Section 8 hereto.

“Person” shall mean any individual, corporation, limited liability company, estate, partnership, joint venture, association, joint stock company, trust (including any beneficiary thereof), unincorporated organization or government or any agency or political subdivision thereof.

“Preference Amount” shall mean any interest on or principal of the Class A Notes which has become Due for Payment, the Nonpayment of which would have been covered by the Policy, and which was made to a Holder by or on behalf of the Issuing Entity which has been deemed a preferential transfer and recoverable, or theretofore recovered, from its Holder pursuant to the Bankruptcy Code in accordance with a final, nonappealable order of a court of competent jurisdiction; provided that any Preference Amount that constitutes interest shall be limited to the amount of interest on the outstanding principal amount of the Class A Notes (calculated at the Interest Rate for the relevant class of Class A Notes) accrued as of the last day of the applicable interest accrual period with respect to the Class A Notes and shall not, in any event, include any interest on the Class A Notes accrued after such date or any interest on such interest amount; provided, further, that in no event shall Ambac be obligated to make any payment in respect to any Preference Amount to the extent that such payment, when added to all prior payments of Policy Claim Amounts, would exceed the Maximum Insured Amount.

“Preference Payment Date” shall have the meaning given such term in Section 8 hereto.

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“Reimbursement Amount” shall mean, as of any Distribution Date, the sum of (x)(i) all Insured Payments paid by Ambac, but for which Ambac has not been reimbursed prior to such Distribution Date, plus (ii) interest accrued on such Insured Payments not previously repaid calculated at the Late Payment Rate from the date the Indenture Trustee, or any other Person at its direction, received the related Insured Payments or the date such Insured Payments were made, and (y) without duplication (i) any amounts then due and owing to Ambac under the Insurance Agreement, the Indenture and the Sale and Servicing Agreement, as certified to the Indenture Trustee by Ambac plus (ii) interest on such amounts at the Late Payment Rate.

“Sale Agreement” shall mean the Sale Agreement between UACC and the Seller, dated as of December 1, 2006, as such Sale Agreement may be amended from time to time.

“Sale and Servicing Agreement” shall mean that certain Sale and Servicing Agreement, dated as of December 1, 2006, by and among the Issuing Entity, the Seller, the Servicer, the Trust Collateral Agent, the Custodian, the Backup Servicer and the Designated Backup Subservicer, as the same may be amended or supplemented from time to time.

“Scheduled Payments” shall mean, with respect to any Distribution Date, an amount equal to the sum of the Noteholders’ Interest Distributable Amount (net of any interest shortfalls resulting from the application of Relief Act Shortfalls) and the Noteholders’ First Principal Distributable Amount (other than the amount specified in clause (2)(b) of the definition thereof) for the related Distribution Date; provided that Scheduled Payments shall not include (x) any portion of a Noteholders’ Interest Distributable Amount or of a Noteholders’ Interest Carryover Amount due to Holders because the Notice in proper form was not timely received by Ambac, or (y) any portion of a Noteholders’ Interest Distributable Amount due to Holders representing interest on any prior unpaid Noteholders’ Monthly Interest Distributable Amount. For the avoidance of doubt, the Noteholders’ Interest Distributable Amount shall be determined after giving effect to any prior payments made by Ambac under this Policy.

“Seller” shall mean UPFC Auto Financing Corporation, a Texas corporation, and its successors and assigns.

“Servicer” shall mean United Auto Credit Corporation, a California corporation, and its successors and assigns.

“Spread Account” shall mean the account designated as such, established and maintained pursuant to the Spread Account Agreement.

“Spread Account Agreement” shall mean the Spread Account Agreement, dated as of December 14, 2006, among the Insurer, the Indenture Trustee and the Servicer.

“Trust Accounts” shall have the meaning assigned thereto in Section 5.1 of the Sale and Servicing Agreement.

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“Trust Agreement” shall mean the Trust Agreement dated as of November 17, 2006 between the Seller and Wells Fargo Delaware Trust Company, not in its individual capacity but solely as Owner Trustee, as amended and restated as of December 14, 2006, as the same may be amended or supplemented from time to time.

“UACC” shall mean United Auto Credit Corporation, a California corporation.

“United Party” shall mean any of the Issuing Entity, the Servicer, UACC, the Seller and any of their respective Affiliates.

2. Payments under the Policy.

(a) Upon the presentation by the Indenture Trustee to Ambac at Ambac’s principal office in respect of the applicable Distribution Date of a duly executed Notice, Ambac will make or cause to be made to the Indenture Trustee, on the guarantee set forth in the first paragraph of this Policy, payment in an amount equal to the applicable Policy Claim Amount.

(b) Amounts payable in respect of any Policy Claim Amounts due hereunder, unless otherwise stated herein, will be distributed by Ambac to, or at the direction of, the Indenture Trustee, by wire transfer of immediately available funds. Solely the Indenture Trustee on behalf of the Holders shall have the right to make a claim for Policy Claim Amounts under this Policy.

(c) Ambac’s payment obligations hereunder with respect to particular Policy Claim Amounts shall be discharged to the extent funds equal to the applicable Policy Claim Amounts are paid by Ambac to, or at the direction of, the Indenture Trustee in accordance with the Indenture Trustee’s requests, whether or not such funds are properly applied by the Indenture Trustee. Payments of Policy Claim Amounts shall be made only at the time set forth in this Policy, and no accelerated Insured Payments shall be made except to the extent that Ambac has specified an earlier date for payment at its sole option. This Policy does not insure against loss of any prepayment or other acceleration payment which at any time may become due in respect of any Insured Obligations, other than at the sole option of the Insurer, nor against any risk other than Nonpayment, including failure of the Indenture Trustee to pay any Policy Claim Amounts or Scheduled Payments due to Holders.

(d) Notwithstanding anything to the contrary set forth herein, in no event shall the aggregate amount paid by Ambac hereunder exceed the Maximum Insured Amount hereunder.

3. Presentation of Notice of Non-Payment and Demand.

(a) Notwithstanding any other provision of this Policy but subject to Section 8 hereof with respect to Preference Amounts, the Insurer will pay any Policy Claim Amounts payable hereunder other than with respect to Preference Amounts to, or at the direction of, the Indenture Trustee no later than 12:00 noon, New York City time, on the later of (i) the Distribution Date on which the related Policy Claim Amount is due for

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payment under the Indenture or (ii) the second Business Day following actual receipt in New York, New York on a Business Day by the Insurer of a Notice in the form attached as Exhibit A, appropriately completed and executed by the Indenture Trustee; provided that, if such Notice is received after 12:00 noon, New York City time, on such Business Day, it will be deemed to be received before 12:00 noon on the following Business Day.

(b) If any such Notice is not in proper form or is otherwise insufficient for the purpose of making a claim under this Policy, it shall be deemed not to have been received by the Insurer for purposes of this Policy, and the Insurer shall promptly so advise the Indenture Trustee in writing and the Indenture Trustee may submit an amended or corrected Notice. If such an amended or corrected Notice is in proper form and is otherwise sufficient for the purpose of making a claim under this Policy, it shall be deemed to have been timely received on the Business Day of such resubmission subject to the proviso in (a) above.

4. Waiver. Ambac hereby waives and agrees not to assert any and all rights to require the Indenture Trustee to make demand on or to proceed against any Person, party or security prior to demanding payment under this Policy. For the avoidance of doubt, Ambac does not waive its right to seek payment of all Reimbursement Amounts to which it is entitled.

5. Subrogation. Upon any payment hereunder, in furtherance and not in limitation of Ambac’s equitable right of subrogation and Ambac’s rights under the Insurance Agreement, Ambac will, to the extent of such payment by Ambac hereunder, be subrogated to the rights of any Holder to receive any and all amounts due in respect of the Insured Obligations as to which such Insured Payment was made, to the extent of any payment by Ambac under this Policy and Ambac will be a co-beneficiary of the Indenture Trustee’s lien under the Indenture.

6. Communications. All notices, presentations, transmissions, deliveries and communications made by the Indenture Trustee to Ambac with respect to this Policy shall specifically refer to the number of this Policy and shall be made to Ambac at:

or to such other address, officer, telephone number or facsimile number as Ambac may designate to the Indenture Trustee from time to time.

7. Nature of the Obligations. Except as expressly provided herein, the obligations of Ambac under this Policy are irrevocable, absolute and unconditional.

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8. Preference Payments. The Insurer shall pay any Preference Amount when due to be paid pursuant to an Order referred to below, but in any event no earlier than the fifth Business Day following actual receipt by the Insurer of (i) a certified copy of the final, nonappealable order of a court or other body exercising jurisdiction to the effect that a Holder is required to return such Preference Amount paid during the term of this Policy because the payments of such amounts were avoided as a preferential transfer or otherwise rescinded or required to be restored by the Indenture Trustee or such Holder (the “Order”), (ii) an opinion of counsel satisfactory to the Insurer stating that the Order has been entered and is final and not subject to any stay, (iii) an assignment, in form and substance satisfactory to the Insurer, duly executed and delivered by such Holder and the Indenture Trustee, irrevocably assigning to the Insurer all rights and claims of the Indenture Trustee and such Holder relating to or arising under the Indenture or otherwise with respect to such Preference Amount, (iv) appropriate instruments in form satisfactory to the Insurer to effect the appointment of the Insurer as agent for the Indenture Trustee and such Holder in any legal proceeding related to such Preference Amount, and (v) a Notice (in the form attached as Exhibit B) appropriately completed and executed by the Indenture Trustee (the “Preference Payment Date”); provided, that (I) if such documents are received by the Insurer after 12:00 noon, New York City time, on such Business Day, they will be deemed to be received on the following Business Day, (II) the Insurer shall not be obligated to pay any Preference Amount in respect of principal (other than the amount set forth in clause (i) of the definition of Noteholders’ First Principal Distributable Amount) prior to the Final Scheduled Distribution Date for the relevant class of Class A Notes and (III) any Preference Amount that constitutes interest shall be limited to the amount of interest on the Outstanding Amount of the Class A Notes (calculated at the Interest Rate for the relevant class of Class A Notes) accrued as of the last day of the applicable interest accrual period with respect to the Class A Notes and shall not, in any event, include any interest on the Class A Notes accrued after such date or any interest on such interest amount. Such payment shall be disbursed to the receiver, conservator, debtor-in-possession or trustee in bankruptcy named in the Order, and not to the Indenture Trustee or the Holder directly, unless the Indenture Trustee or the relevant Holder has made a payment of the Preference Amount to the court or such receiver, conservator, debtor-in-possession or trustee in bankruptcy named in the Order, in which case the Insurer will pay the Indenture Trustee, or as directed by the Indenture Trustee, to the extent of the payment of the Preference Amount, subject to the delivery of (a) the items referred to in clauses (i), (ii), (iii), (iv) and (v) above to the Insurer and (b) evidence satisfactory to the Insurer that payment has been made to such court or receiver, conservator, debtor-in-possession or trustee in bankruptcy named in the Order.

Notwithstanding the foregoing, in no event shall Ambac be obligated to make any payment in respect of any Preference Amount (i) to the extent that such payment, when added to all prior payments of Insured Payments, would exceed the Maximum Insured Amount or (ii) prior to the time Ambac would have been required to make an Insured Payment pursuant to Section 3 of this Policy.

9. No Acceleration. There shall be no acceleration payment due under this Policy unless such acceleration is at the sole option of the Insurer. This Policy does not cover (i) premiums, if any, payable in respect of the Class A Notes, (ii) shortfalls, if any,

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attributable to any payment of withholding taxes (including penalties and interest in respect of any such liability) or (iii) any risk other than Nonpayment, including the failure of the Indenture Trustee to apply, disburse, transfer or direct Policy payments or Available Funds or other amounts in accordance with the Indenture to Holders or to any other party.

10. Termination. This Policy and the obligations of Ambac hereunder shall terminate upon the first date on which each of the following shall have occurred:

(a) all of the Scheduled Payments have been paid in full;

(b) any period during which any Scheduled Payment could have been avoided in whole or in part as a preference payment under applicable bankruptcy, insolvency, receivership or similar law shall have expired; and

(c) if any proceedings requisite to avoidance as a preference payment have been commenced prior to the occurrence of (a) and (b), a final and nonappealable order in resolution of each such proceeding has been entered.

11. Miscellaneous.

(a) This Policy sets forth the full understanding of Ambac and, except as expressly provided herein, or as otherwise agreed in writing hereafter by Ambac and the Indenture Trustee, may not be canceled or revoked.

(b) This Policy is issued pursuant to, and shall be construed under, the laws of the State of New York, without giving effect to the conflicts of laws rules thereof, as contemplated in Section 5-1401 of the New York General Obligations Law.

(c) THE INSURANCE PROVIDED BY THIS POLICY IS NOT COVERED BY THE PROPERTY/CASUALTY INSURANCE SECURITY FUND SPECIFIED IN ARTICLE 76 OF THE NEW YORK INSURANCE LAW.

(d) Any notice hereunder or service of process on Ambac may be made at the address listed above for Ambac or such other address as Ambac shall specify in writing to the Indenture Trustee.

(e) The premium of this Policy is not refundable for any reason. The premium will be payable on this Policy on each Distribution Date as provided in the Insurance Agreement, beginning with the First Distribution Date.

ANY PERSON WHO KNOWINGLY AND WITH INTENT TO DEFRAUD ANY INSURANCE COMPANY OR OTHER PERSON FILES AN APPLICATION FOR INSURANCE OR STATEMENT OF CLAIM CONTAINING ANY MATERIALLY FALSE INFORMATION, OR CONCEALS FOR THE PURPOSE OF MISLEADING, INFORMATION CONCERNING ANY FACT MATERIAL THERETO, COMMITS A FRAUDULENT INSURANCE ACT, WHICH IS A CRIME AND SHALL ALSO BE SUBJECT TO A CIVIL PENALTY NOT TO EXCEED FIVE THOUSAND DOLLARS AND THE STATED VALUE OF THE CLAIM FOR EACH SUCH VIOLATION.

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IN WITNESS WHEREOF, Ambac has caused this Note Guaranty Insurance Policy to be executed and attested this 14th day of December, 2006.

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EXHIBIT A

TO THE NOTE GUARANTY INSURANCE POLICY

Policy No. AB1053BE

NOTICE OF NONPAYMENT AND DEMAND

FOR PAYMENT OF INSURED AMOUNTS

(OTHER THAN PREFERENCE AMOUNT)

Date:                     

Ambac Assurance Corporation

One State Street Plaza

New York, New York 10004

General Counsel – URGENT

Reference is made to Note Guaranty Insurance Policy No. AB1053BE (the “Policy”) issued by Ambac Assurance Corporation (“Ambac”). Terms capitalized herein and not otherwise defined shall have the meanings specified in the Policy, unless the context otherwise requires.

The undersigned hereby certifies as follows:

ANY PERSON WHO KNOWINGLY AND WITH INTENT TO DEFRAUD ANY INSURANCE COMPANY OR OTHER PERSON FILES AN APPLICATION FOR INSURANCE OR STATEMENT OF CLAIM CONTAINING ANY MATERIALLY FALSE INFORMATION, OR CONCEALS FOR THE PURPOSE OF MISLEADING, INFORMATION CONCERNING ANY FACT MATERIAL THERETO, COMMITS A FRAUDULENT INSURANCE ACT, WHICH IS A CRIME AND SHALL ALSO BE SUBJECT TO A CIVIL PENALTY NOT TO EXCEED FIVE THOUSAND DOLLARS AND THE STATED VALUE OF THE CLAIM FOR EACH SUCH VIOLATION.

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EXHIBIT B

TO THE NOTE GUARANTY INSURANCE POLICY

Policy No. AB1053BE

NOTICE OF NONPAYMENT AND DEMAND

FOR PAYMENT OF PREFERENCE AMOUNT

Date:                     

Ambac Assurance Corporation

One State Street Plaza

New York, New York 10004

General Counsel – URGENT

Reference is made to Note Guaranty Insurance Policy No. AB1053BE (the “Policy”) issued by Ambac Assurance Corporation (“Ambac”). Terms capitalized herein and not otherwise defined shall have the meanings specified in the Policy, unless the context otherwise requires.

The undersigned hereby certifies as follows:

ANY PERSON WHO KNOWINGLY AND WITH INTENT TO DEFRAUD ANY INSURANCE COMPANY OR OTHER PERSON FILES AN APPLICATION FOR INSURANCE OR STATEMENT OF CLAIM CONTAINING ANY MATERIALLY FALSE INFORMATION, OR CONCEALS FOR THE PURPOSE OF MISLEADING, INFORMATION CONCERNING ANY FACT MATERIAL THERETO, COMMITS A FRAUDULENT INSURANCE ACT, WHICH IS A CRIME AND SHALL ALSO BE SUBJECT TO A CIVIL PENALTY NOT TO EXCEED FIVE THOUSAND DOLLARS AND THE STATED VALUE OF THE CLAIM FOR EACH SUCH VIOLATION.

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