| If you expect the S corporation to incur substantial losses in excess of your basis, then these losses would not be deductible on your personal tax return.
If the S corporation obtains a line of credit that is co-signed or guaranteed by you, to support the losses or cash flow, this method does not increase the taxpayers basis per IRS rules.
The best way to increase Basis in an S corporation is obtain a loan personally by the shareholder and then loan this money to the S Corporation. This is referred to as a Back-Back Loan to the S corporation. | 
