<prompt> Human: I received a notice of deficiency for 2013, accepted, and mailed it back to them. The beginning of September I received a notice to pay a total of 208.17 by Monday, September 28. Despite not having a well-paying job, I managed to budget and pay off the debt in full on Friday, September 25. My method of payment was online, redirected to a pay site listed on irs.gov which mentioned that the money may not be received for 5 days after completion of the transaction. I paid off the total and thought it was over. This morning, I awoke to find another letter from the IRS claiming i owe 208.17, plus a failure to pay penalty and interest charges bringing the amount to 209.77. Im hoping its a simple discrepancy over the 5 day waiting period, I know paying right before a weekend doesnt help but I couldnt pay it off until literally the last opportunity I had. I plan to call the IRS when their offices open later today, but wouldnt mind advice if anyones gone through this situation before.  <response>: call them, this is an everyday problem that everyone faces. I just paid my phone bill and it says its still overdue! they send thousands of letters. just common sense really 