You will need to make the payment for all 3 quarters on or before September 15th. You will be hit with the underpayment penalty for the first 2 quarters. If you can, I would suggest paying the taxes for the 2 quarters as soon as possible. Then make the remaining quarters payments on time.
The underpayment tax penalty is worked out by looking:
- How much you owed
- How long it took before you finally paid
https://turbotax.intuit.com/tax-tips/small-business-taxes/estimated-taxes-how-to-determine-what-to-pay-and-when/L3OPIbJNw
@sfallcreek Thanks for the question!!