Correct repayment of a loan is not taxable or a tax deduction, but interest expense is reported by the business and you would have interest income (during the time the loan is held). Learn more about calculating, what's called imputed interest (required) here: https://turbotax.intuit.com/tax-tips/tax-payments/irs-tax-rules-for-imputed-interest/L7UbulHpC
For recording your loan, it will affect your balance sheet and business value (not income and expenses). When you initially put the money in the business, it increased your cash account (asset) and should be recorded to a Loan to shareholder account. Then, payments out of the business bank account are recorded to the loan and will decrease it the balance of the loan.
