Research and Development Tax Credit Expansion Act of 2023 This bill modifies the refundable research tax credit for new and small businesses to (1) provide for an inflation adjustment to the limit on credit refundability; (2) allow refundable amounts to cover all payroll taxes paid by such businesses; and (3) extend eligibility for the credit to small businesses with less than $10 million in gross receipts (currently, less than $5 million). The bill also increases the rate of the alternative simplified tax credit for such businesses.