original_query: What is the formula for calculating the credit for qualified research expenses in the 4th and 5th taxable years?
query: What is the formula for calculating the R&D tax credit for qualified research expenses in the 4th and 5th taxable years under the Start-up Credit Calculation?
answer: For the 4th and 5th taxable years, the fixed-base percentage is 3% each year.  In the 6th year, it's 1/6th of the percentage that the aggregate qualified research expenses of the 4th and 5th years are of the aggregate gross receipts for those years.