Inputs you will need

To run prejudgment or post-judgment interest for New York in DocketMath’s interest calculator, you’ll need to gather a small, consistent set of inputs.

Use this as a checklist:

• Jurisdiction: New York (US-NY)
• Interest type

  • Prejudgment interest
  • Post-judgment interest
  • Mixed / segmented (part before judgment, part after)
• Principal amount(s)

  • Dollar amount owed
  • Whether the amount changes over time (multiple principal entries)
• Accrual start date(s)

  • Date interest begins to run on each amount
• End date

  • Through-date for interest (e.g., “today,” “through filing,” “through judgment”)
• Judgment date (if applicable)
• Rate selection method

  • Statutory default rate (e.g., CPLR-based)
  • Contract rate
  • Other court-ordered rate
• Contract or order rate (if not statutory)

  • Annual rate (e.g., 9%, 5.25%)
  • Whether the rate changes over time
• Compounding details (if any)

  • Simple interest (no compounding)
  • Compounding frequency (annual, monthly, etc.), if ordered or agreed
• Allocation across claims or periods (optional, but often useful)

  • Separate principal and start date for each claim, invoice, or time slice
• Rounding and display preferences

  • Rounding to cents vs. whole dollars
  • Whether to show daily rate and per-period breakdown

How these inputs affect the output

Understanding how each input changes the result will help you sanity-check the output:

• Jurisdiction (US-NY)
  This tells DocketMath to:

  • Use New York-specific defaults where available (e.g., statutory rate presets when appropriate).
  • Apply New York-friendly date rules (e.g., inclusive/exclusive handling consistent with typical NY practice).

• Interest type

  • Prejudgment: Interest runs from a chosen start date up to the judgment date.
  • Post-judgment: Interest runs from the judgment date forward.
  • Mixed: You may have one rate and period before judgment and another after; DocketMath can segment that.

• Principal amount & changes over time

  • A single principal with one start date gives a straightforward calculation.
  • Multiple principal entries (e.g., several invoices or periodic underpayments) can materially increase or decrease total interest because each amount accrues over a different period.

• Accrual start date

  • Moving the start date earlier increases interest; moving it later decreases it.
  • For multiple items, each start date creates its own accrual “track.”

• End date

  • The longer the period between start and end date, the more interest accrues.
  • You can re-run the same scenario with different end dates to compare “interest through settlement” vs. “interest through trial,” etc.

• Rate selection method

  • Statutory default: DocketMath applies the New York statutory rate preset (where applicable for your interest type) so you don’t have to manually enter the percentage.
  • Contract rate: You enter the rate from the agreement; the output will change significantly if the contract rate is higher or lower than the statutory default.
  • Court-ordered rate: If a judge specifies a rate, you can enter it directly.

• Compounding

  • Simple interest: Interest is calculated only on principal.
  • Compound interest: Interest is periodically added to principal, so you earn “interest on interest,” increasing the total—sometimes dramatically over long periods or high rates.
  • If New York law or a contract calls for simple interest only, be sure to set that explicitly.

• Allocation across claims or periods

  • Breaking things out by claim, invoice, or time period lets you:

    • See which items drive the most interest.
    • More easily adjust if the court disallows interest on a particular component.

• Rounding & display

  • Rounding to cents vs. dollars can matter in large, multi-year calculations.
  • Showing daily rates or per-period breakdowns can make your work more transparent to opposing counsel or the court.

Where to find each input

Below is a practical guide to where these inputs usually live in a New York matter. This is not exhaustive, but it covers the most common sources.

Jurisdiction (US-NY) and interest type

You can usually confirm this from:

• Caption of the case (New York state court vs. federal court applying New York law).
• Engagement memo or internal matter summary.
• Pleadings describing whether you’re seeking prejudgment, post-judgment, or both.

Principal amount(s)

Look to:

• Complaint, bill of particulars, or amended pleadings.
• Settlement demand letters or mediation statements.
• Invoices, account statements, or loan ledgers.
• Stipulations or partial settlement agreements (for narrowed principal).

If principal changes over time (e.g., partial payments, adjustments, or multiple invoices):

• Use:

  • Payment histories.
  • Accounting system exports (CSV/Excel).
  • Bank statements, if necessary.

Accrual start date(s)

Common sources:

• Contract provisions (e.g., “interest shall accrue on unpaid amounts 30 days after invoice”).
• Statutory references in the complaint or motion papers.
• Court orders specifying when interest begins.
• For tort or other non-contract claims, the date of:

  • Breach
  • Injury
  • Demand
  • Or another legally significant event

Because New York rules on start dates can be nuanced, treat this as a legal judgment call, then plug that date into DocketMath.

End date

Decide what you want the calculation to show:

• Through filing date: Use the date you file a motion or pleading.
• Through judgment date: Use the date of entry of judgment.
• Through a projected settlement date: Use a future date to estimate exposure.

You’ll typically find the judgment date in:

• The judgment itself (clerk-stamped date).
• Docket entries in NYSCEF or the relevant court system.

Judgment date

If you are calculating:

• Prejudgment interest: Judgment date is the end of the prejudgment period.
• Post-judgment interest: Judgment date is the start of the post-judgment period.

Sources:

• NYSCEF docket sheet or eCourts printout.
• Certified copy of judgment.
• Internal case management system capturing the entry date.

Rate selection method and rate

Statutory rate (New York)

If you’re using a statutory rate:

• Check:

  • CPLR provisions or other New York statutes referenced in your pleadings or motion.
  • Any court decisions in the case that mention the applicable rate.

DocketMath’s New York preset helps avoid manual entry, but you should still confirm that statutory interest is what you’re actually seeking for that claim type.

Contract rate

Look for:

• Interest clause in the contract (often in payment, default, or remedies sections).
• Amendments or riders that modify the rate.
• For revolving accounts or loans, any rate change notices.

Record:

• The annual rate (not just “1.5% per month”—convert to 18% annually, or enter the equivalent setting).
• Any step changes (e.g., 6% for first year, then 9%).

Court-ordered rate

If a court sets or modifies the rate:

• Use:

  • Orders on summary judgment, damages, or post-trial motions.
  • Appellate decisions remanding with instructions on interest.

Compounding (if any)

In New York, interest is often simple unless the contract or statute says otherwise, but you must confirm:

• Contract terms:

  • Look for language like “interest shall be compounded monthly” or “interest shall accrue on unpaid interest.”
• Court orders:

  • Some orders expressly allow or disallow compounding.

If nothing clearly authorizes compounding, many practitioners default to simple interest—but that’s a legal judgment you must make outside the calculator.

Allocation across claims or periods

You’ll usually build this from:

• A damages spreadsheet breaking out:

  • Principal by claim (breach of contract count, unjust enrichment, etc.).
  • Principal by invoice or date.
• Expert or accountant reports.
• Internal models used for settlement analysis.

Each row in your spreadsheet can map to a separate principal entry in DocketMath, with its own start date.

Rounding and display preferences

These are more about presentation than law:

• Internal practice guidelines (e.g., “always round to cents”).
• Court preferences, if any (some judges dislike over-precise decimals).
• Your own need for:

  • A one-line total
  • Versus a detailed schedule (for exhibits or expert reports)

Run it

Once you’ve gathered your inputs, you can run the calculation in DocketMath’s interest tool in a repeatable way:

1. Select jurisdiction

   • Choose New York (US-NY) so the calculator applies the correct presets and labeling.

2. Choose interest type

   • Pick prejudgment, post-judgment, or both, depending on your scenario.
   • If you have both prejudgment and post-judgment periods, set them up as separate segments so you can apply different dates and rates as needed.

3. Enter principal amounts and start dates

   • Add one line for each lump sum, invoice, or damages component.
   • For each line, enter the principal and its accrual start date.

Inputs you will need

Use this checklist to gather the core inputs before you run the Interest tool.

• principal or judgment amount
• interest type (pre- or post-judgment)
• rate and compounding method
• start date and end/as-of date
• payments or credits that reduce principal
• day-count convention

Where to find each input

Most inputs live in the case file, contracts, or docket entries. Dates usually come from the triggering event notice; rates and caps come from governing documents or statute; and amounts come from the ledger or judgment. Record the source for each value so the run is reproducible.

Run it

Enter the inputs in DocketMath and run the Interest calculation to generate a clean breakdown: Run the calculator.

If an assumption is uncertain, document it alongside the calculation so the result can be re-run later.

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

Related reading

• Worked example: deadlines in New York

• Interest rule lens: Maine

• Inputs you need for deadlines in Australia

• Why we started the DocketMath blog