Why interest results differ in New Hampshire

New Hampshire post-judgment interest looks deceptively simple—until your number doesn’t match the other side’s spreadsheet, the clerk’s figure, or a prior order.

This guide walks through the most common reasons interest results differ in New Hampshire and how to quickly diagnose the mismatch using DocketMath’s interest calculator.

The top 5 reasons results differ

In New Hampshire, small differences in assumptions can produce large swings in total interest. When two calculations don’t match, it’s usually one (or more) of these:

• Different trigger dates or event definitions were used.
• Inputs were entered with different day-count or compounding assumptions.
• Payments, credits, or tolling periods were handled differently.
• Jurisdiction or court settings did not match the matter.
• Rounding or cutoff-time rules were applied inconsistently.

1. Wrong annual rate (or wrong time period for the rate)

New Hampshire’s statutory post-judgment interest rate has changed over time and is often tied (directly or indirectly) to external benchmarks.

Common rate problems:

• Using today’s rate for a judgment entered years ago
• Applying one flat rate across the entire life of the judgment when the statute changed mid-stream
• Relying on a contract rate when New Hampshire law requires a different statutory rate for judgments

In DocketMath, even a 0.5–1% rate difference can move the total by thousands of dollars on a large judgment.

Diagnostic clue:
If your total interest is consistently higher or lower by roughly the same percentage across all date ranges, the annual rate is your primary suspect.

2. Simple vs. compound interest

New Hampshire law may call for simple interest in many contexts, but:

• The other side may be compounding annually or monthly
• Someone may be “rolling” prior unpaid interest into the principal and then applying a simple rate to that larger number (effective compounding)
• A prior order might have specified a different methodology

In DocketMath’s interest tool, this is controlled by:

• Interest type: simple vs. compound
• Compounding frequency (if compound is selected): annually, quarterly, monthly, etc.

Diagnostic clue:
If your daily rate looks right but the long‑term total (over years) is off by a noticeable margin, check whether one side is compounding and the other is not.

3. Principal changes: partial payments, fees, and costs

Interest is only as accurate as the principal you’re applying it to. Differences often arise because:

• One party applies payments to principal first; the other applies them to interest first
• Attorney’s fees or costs are added to principal on different dates (or not at all)
• A lump-sum “principal” figure already includes some interest from a prior period, and then interest is charged again (double-counting)

In DocketMath, you can model:

• Principal as of judgment date
• Adjustments (payments or additions) with specific effective dates

Diagnostic clue:
If your interest matches for the early part of the schedule but diverges after certain payments or fee awards, the issue is almost always the payment application rules or timing of added amounts.

4. Date conventions and counting rules

Even when everyone agrees on the rate and principal, dates can quietly derail the math:

• Start date:

  • Are you starting interest on the date of judgment, or the day after?
  • Are you using a pre-judgment date (e.g., breach date, verdict date) instead?
• End date:

  • Through the date of payment, or through the date of a specific order?
  • Inclusive vs. exclusive of the end date?
• Leap years and day-count conventions:

  • Using 365 vs. 366 vs. “actual/365” vs. “actual/actual”

In DocketMath, the interest calculator uses explicit From and To dates and a consistent day-count method. If another calculation uses a different convention, you’ll typically see:

• A small mismatch that grows linearly with time (e.g., off by a few dollars per year)

Diagnostic clue:
If the difference between two calculations grows roughly in proportion to the number of days, and everything else looks right, you likely have a start/end date or day-count mismatch.

5. Ignoring (or misreading) New Hampshire–specific rules

New Hampshire has its own statutory and case-law framework for:

• What rate applies (and from when)
• Whether the rate is fixed or variable
• How to treat different kinds of judgments or claims

Common practical issues:

• Applying the wrong statute (e.g., using a general civil rate for a special category of claim)
• Assuming a floating rate when the applicable New Hampshire rule is fixed (or vice versa)
• Missing a court order that modifies the default statutory approach

Diagnostic clue:
If your math and inputs are identical but someone insists on a different rate or start date “because New Hampshire law says so,” you may be dealing with a legal-interpretation difference, not a calculator error.

How to isolate the variable

When numbers don’t match, treat it like debugging.

• Freeze the jurisdiction and tool settings so both runs use the same rule set.
• Compare one input at a time (dates, rates, amounts) and re-run after each change.
• Review the breakdown to see which segment or assumption drives the difference.

Step 1: Lock in the shared facts

Start by agreeing on these, in writing if possible:

• Judgment amount (principal only)
• Judgment date
• Evaluation end date (e.g., “through 12/31/2025”)
• List of payments (amount + date)
• Any additional amounts added to principal (fees, costs, etc.) and their dates

Enter only these shared facts into DocketMath’s interest calculator and use:

• One fixed rate
• Simple interest
• No compounding

Once your counterpart can reproduce this “baseline” number, you’ve confirmed the core data.

Step 2: Change one knob at a time

Next, adjust each of these, one by one, and compare:

1. Annual rate

   • Increase or decrease the rate to match the other side’s claimed percentage.
   • If the totals now match, the dispute is about which rate applies, not about the math.

2. Interest type and compounding

   • Switch from simple to compound; try annual compounding first.
   • If that closes the gap, you’ve identified a compounding mismatch.

3. Payment application rules

   • In DocketMath, model payments as reducing principal on the payment date.
   • If the other side applies payments to interest first, manually simulate that and compare.

4. Start and end dates

   • Shift the start date by one day earlier or later.
   • Adjust the end date by one day.
   • If the difference moves by roughly one day’s worth of interest, it’s a date-counting issue.

5. Segmented or changing rates

   • Use multiple periods with different rates (e.g., rate A until a statute change date, rate B after).
   • If this matches the other side’s number, you’ve confirmed they’re using a time-varying rate.

Step 3: Document your settings

Once you’ve matched (or confidently isolated) the difference:

• Export or screenshot the DocketMath settings
• Label each assumption clearly (e.g., “Simple interest at X% from judgment date to payment date”)
• Keep a short narrative explaining any New Hampshire–specific choices (e.g., “Rate based on [statute/case] as interpreted by counsel”)

This makes it easier to explain your math to co-counsel, clients, or the court without re-running the entire analysis.

Next steps

When your New Hampshire interest numbers don’t match:

1. Confirm the legal framework

   • Identify which New Hampshire statute, rule, or order you’re relying on for:

     • Rate
     • Start date
     • Simple vs. compound interest
   • Ask opposing counsel (or the clerk) to identify theirs, in writing.

2. Rebuild the calculation in DocketMath

   • Start with the simplest shared version (fixed rate, simple interest, agreed principal and dates).
   • Layer in payments, fees, and any segmented rates.
   • Use Explain++-style step breakdowns to walk through date ranges and interest accruals.

3. Create comparison scenarios

   • Scenario A: Your interpretation of New Hampshire law
   • Scenario B: Their interpretation
   • Scenario C: Any compromise or court-directed approach
   • Present all three with identical underlying data but different assumptions.

4. Use the tool as a neutral reference in negotiations

   • Emphasize that DocketMath is just doing the arithmetic; the real debate is over which legal inputs are correct.
   • This often de-escalates “your spreadsheet vs. mine” arguments.

To experiment with your own fact pattern, start a clean run in the DocketMath interest calculator and walk through the inputs above.

Related reading

• Why we started the DocketMath blog

• Introducing Explain++: step-by-step calculation breakdowns

• Why we started the DocketMath blog

• Why we started the DocketMath blog