Just for I fun thought I would try the EFTPS "telephone payment" option. (You still need an account and login but there is a phone number on the main page of EFTPS for "pay by phone"). So I called this number and went through the prompts to make my payment and guess what? There was no prompt to enter which month to apply your payment to. It only asks for tax form, tax year, type of payment (there is an option for deferred social security tax) and amount of payment. Later I checked payment history on my EFTPS account and the payment was there. Whether it gets applied properly is yet to be seen but I fulfilled my obligation.
