Copy from the Authorization. SBA Lenders may use this form.This Form is to be used for all sales of the guaranteed portion of a 7(a) loan in the SBA Secondary Market. About this document and download. Supplemental Loan Agreement SBA Express Program. SBA Form 148 (Unconditional Guarantee) and SBA Form 148L (Limited Guarantee) are the standard documents for providing a guaranty on an SBA loan. SBA disaster loan application form on the wooden surface. Check out the options below and connect with an advisor for more information. Complete Guide to Entity and Guarantor Documentation for SBA 7(a) Loans. To fill out this form, first ensure you have all necessary information at hand, including loan details and personal identification.