Instant Interest Release Notes Version

Program Changes

This release adds a new field, Taxpayer State, to the input panels. This field is used to determine eligibility for payment extensions in cases where the financial presence of a business in a state is a factor in determining eligibility. It does not apply to cases where blanket extensions are granted, as was the case in 2020 when tax relief was granted to all taxpayers due to the coronavirus (COVID-19) pandemic. In 2021 the IRS and the states of Louisiana, Oklahoma, and Texas granted payment extensions for businesses with financial operations in those three states due to the severe winter storms that occurred there. What constitutes financial operations that qualify a business to receive the automatic extensions varies by jurisdiction. Customers should consult the respective declarations to determine eligibility:

If the Jurisdiction for which payment is due and the Taxpayer State match an entry in the new Extensions table now incorporated into Instant Interest and the due date falls in the range of dates for which the extension is granted, the extension will be automatically applied. You can view the extensions that are currently available by clicking the “Extensions” button at the bottom right of the input panel.


  1. An extension is applied only on the Standard Input panel. Since dates on the Easy Calculation and Custom Calculation are fully under user control, the assumption is that the dates entered are the ones to be used in calculating an interest schedule.
  2. Recent updates have involved large scale coding changes to Instant Interest. If you encounter any problems, either with navigation or calculations, please let us know by emailing

Rate Changes

The following rate change is implemented in this version of Instant Interest effective April 1, 2021:

  • Missouri changed from 1.2% to 0.9% for overpayments; the rate for underpayments remained 3.0%.

The following changes re implemented retroactively to January 1, 2021:

  • California changed from 5.0% to 3.0% for underpayments; the rate for overpayments remained 0.0%.
  • Maryland changed from 10.5% to 10.0% for both underpayments and overpayments.
  • Montana changed from 8.0% to 6.25% for both underpayments and overpayments (based on a follow-up email).
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