Common interest mistakes in New Hampshire

Running interest in New Hampshire looks simple—until a judge, adjuster, or opposing counsel asks, “Show me how you got that number.”

This post walks through the most common New Hampshire–specific mistakes we see when people calculate interest, and how to avoid them using DocketMath’s /tools/interest calculator.

None of this is legal advice; it’s a practical checklist so you can test your own calculations and talk more clearly with counsel or the court.

The top mistakes

• using the wrong start date for the interest period
• mixing contract rates with statutory rates
• forgetting to reduce principal after payments
• switching between simple and compound assumptions midstream

Capture the source for each input so another team member can verify the same result quickly.

1. Using the wrong interest rate (statutory vs. contract vs. judgment)

New Hampshire has multiple possible interest rates depending on:

• What kind of claim you have
• Whether there’s a contract rate
• Whether you’re pre‑judgment or post‑judgment

Common errors:

• Applying a generic “6%” or “10%” without checking if:

  • A contract sets a specific rate
  • A statute sets a special rate for that type of claim
  • A court order has already specified a rate
• Not updating the rate when a pre‑judgment claim turns into a judgment (or when a court modifies the rate).

How this shows up in numbers:

• On a $50,000 claim over 3 years:

  • At 4% simple interest: about $6,000
  • At 8% simple interest: about $12,000

A wrong rate can easily double the claimed interest.

2. Getting the start date wrong

Interest in New Hampshire often runs from:

• The date of breach or default
• The date a demand was made
• The date the complaint was filed
• The date of judgment

But people routinely:

• Start interest from invoice date even when the contract or law points to a different trigger
• Use the accident date instead of the demand/notice date in tort cases
• Start post‑judgment interest from the hearing date instead of the judgment entry date

Why it matters:

• On $100,000 at 6% simple interest:

  • One year = about $6,000
  • Two years = about $12,000

A one‑year error in the start date is a five‑figure swing on a six‑figure claim.

3. Stopping interest too early (or too late)

Another frequent error is picking the wrong end date:

• Stopping interest on:

  • The date of verdict instead of judgment entry
  • The date you send a demand letter instead of the date of actual payment
• Continuing to run interest:

  • Past the date the principal was fully paid
  • Past the date a court order cut off interest

In negotiations, parties often say “as of today” but then:

• Forget to update the “as of” date later, or
• Keep using the same interest figure months later

DocketMath’s interest calculator makes this explicit: you choose a “through” date, and the output changes immediately if you move that date.

4. Mixing up simple and compound interest

New Hampshire interest is often simple, not compound, unless:

• A contract explicitly provides for compounding, or
• A specific statute or order says otherwise

Common mistakes:

• Letting a spreadsheet compound annually or monthly by default
• Assuming that “interest on interest” is always allowed
• Applying compound interest even when you’re trying to model a court‑style simple‑interest calculation

Impact on outputs:

• $25,000 over 5 years at 8%:

  • Simple interest: $10,000 (total $35,000)
  • Annual compounding: about $11,733 (total ≈ $36,733)

On larger or older claims, the difference gets much bigger.

5. Ignoring partial payments and credits

New Hampshire claims often involve:

• Interim payments
• Settlements with one of several defendants
• Periodic wage or benefit payments

Common errors:

• Calculating interest on the original principal as if no payments were ever made
• Applying all payments only at the end, instead of when they were actually received
• Failing to specify whether a payment goes to:

  • Interest first, then principal, or
  • Principal first, then interest

Each approach creates different outputs:

• If $10,000 is paid early, interest afterward runs on a smaller balance
• If $10,000 is applied late, interest accrues on a larger balance for longer

6. Using calendar years instead of exact day counts

Many New Hampshire interest rules expect day‑by‑day calculations, often based on:

• 365 days per year, or
• “Actual/365” or “Actual/Actual” day‑count methods

Common shortcuts that cause error:

• Treating every year as 365 days, ignoring leap years
• Treating every month as 30 days
• Rounding the time period to the nearest whole year or half‑year

Effect on the numbers:

• Over a decade, leap years and rounding can produce interest differences that:

  • Are small per year, but
  • Become material when the principal is large

DocketMath’s interest tool uses exact dates, so your output changes if you:

• Move the start date by one day
• Move the end date by one day

This often reveals hidden assumptions in manual spreadsheets.

7. Not documenting the calculation method

In New Hampshire disputes, you’re often asked to show your work:

• Opposing counsel may want to replicate your math
• A judge may ask how you got from the principal to the total
• A client or claims committee may need to audit the numbers

Common problems:

• Only saving the final interest figure, not the steps
• Relying on a black‑box spreadsheet that no one else understands
• Forgetting which:

  • Rate you used
  • Day‑count method you assumed
  • Start and end dates you picked
  • Treatment of partial payments you chose

DocketMath’s /tools/interest calculator is designed to be explainable: you can re‑run the calculation, export the steps, and adjust inputs in front of the other side.

How to avoid them

Use this as a practical checklist whenever you run interest on a New Hampshire matter.

Use a written checklist for inputs, document each source, and run a quick sensitivity check before finalizing the result. When two runs differ, compare inputs line by line and re-run with one variable changed at a time.

1. Lock in the correct rate

Before you touch a calculator:

Then, in DocketMath:

• Select the interest type (simple vs. compound) that matches the contract or rule
• Enter the exact rate (e.g., 6.5%, not “about 6%”)

2. Define clear start and end dates

Clarify with your team or counsel:

• What event starts interest?

  • Breach date
  • Demand letter date
  • Complaint filing date
  • Judgment entry date
• What event stops interest?

  • Payment date
  • Judgment date
  • A specific cutoff in an order or settlement

Then:

3. Decide on simple vs. compound (and how often)

With DocketMath, you can choose:

• Simple interest (most court‑style calculations)
• Compound interest with:

  • Annual
  • Quarterly
  • Monthly
  • Daily compounding (if you truly need it)

To keep your math defensible:

• The compounding frequency
• Where that rule comes from (contract, statute, order)

4. Build payments and credits into the timeline

When there are partial payments:

1. List each payment with:

   • Date
   • Amount
   • Whether it should hit interest first or principal first
2. In DocketMath, enter these as dated payments so the tool:

   • Recalculates the remaining principal after each payment
   • Stops interest on amounts that have been paid

This lets you compare:

• A model where payments go to interest first
• A model where payments go to principal first

You can then see how each method changes the total interest.

5. Use exact dates and let the tool handle day counts

Instead of hand‑waving “about three years”:

• Enter the exact dates (e.g., 03/15/2020 to 08/02/2023)
• Let DocketMath handle:

  • Leap years
  • Irregular months
  • Actual day counts

If you’re checking someone else’s spreadsheet:

• Recreate their start date, end date, and rate in DocketMath
• Compare the outputs; differences often reveal:

  • Wrong date assumptions
  • Unintended compounding
  • Rounded time periods

6. Export or save your calculation method

To make your New Hampshire interest math easier to defend:

• Principal amount(s)
• Rate and interest type (simple/compound + frequency)
• Start and end dates
• All payments with dates and allocation rules

Related reading

• Deadlines reference snapshot for New Hampshire

• Interest rule lens: Maine

• Common deadlines mistakes in Australia

• Why we started the DocketMath blog