Interest rule lens: Maine

The rule in plain language

In Maine, “interest” in litigation usually comes up in two places:

1. Prejudgment interest – interest that accrues on a claim before the court enters judgment.
2. Post-judgment interest – interest that accrues after the judgment is entered until it’s paid.

The exact rules depend on:

• What kind of case it is (civil vs. small claims, contract vs. tort, etc.)
• Whether there was a written contract specifying an interest rate
• The year the case or claim “starts” for interest purposes

Because Maine’s interest rules are statute‑driven and change over time, you always need to anchor your calculation to:

• The relevant start date (often the date the complaint is filed or the date of notice)
• The type of claim
• The statutory rate in effect at that time, or
• The rate agreed to in a contract, if enforceable

Because the governing statutes and rates can shift over time—and because some details are nuanced—this post focuses on:

• The conceptual framework for Maine interest,
• The inputs you’ll typically need, and
• How a tool like DocketMath’s interest calculator can help you apply the rules consistently.

Why it matters for calculations

Small differences in the rule text can change the output materially. Using the correct jurisdiction and effective date ensures the calculation aligns with the authority that applies to your matter.

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

1. Prejudgment vs. post-judgment interest

From a calculation perspective, you’re usually dealing with two distinct phases:

Phase	Period covered	Who sets the rate?	Typical trigger date
Prejudgment interest	From a statutory “start” date to judgment	Maine statutes / sometimes contract	Often filing date or notice date
Post-judgment interest	From judgment entry until payment/satisfaction	Maine statutes / sometimes contract	Date judgment is entered on the docket

You may need to:

• Apply one rate for prejudgment interest,
• Apply a different rate for post‑judgment interest, and
• Possibly apply different rates in different years if the statutory rate is variable.

2. Contract vs. non‑contract claims

In Maine, interest can be:

1. Contractual interest – a rate agreed in a written contract (e.g., 12% per year on unpaid balances).
2. Statutory interest – a default rate set by Maine law when the contract is silent or when the claim is not based on a contract (e.g., tort, statutory claims).

For calculations, that means you need to ask:

• Does a written agreement specify an interest rate?
• If so, is that rate enforceable under Maine law (not usurious, not barred by statute)?
• If not, which statutory provision applies to this type of claim?

3. Picking the correct start date

The start date for interest in Maine is not always the same as:

• The date of injury
• The date of breach
• The date of the invoice

Depending on the statute and case type, the interest “clock” might start:

• When the complaint is filed
• When a notice of claim is served
• When the debt becomes due under a contract
• On another specific date set by statute or court order

For your calculation, you typically must choose:

• A principal start date – when the principal amount becomes interest‑bearing
• A judgment date – the date of the court’s judgment
• A payment date – the date you want to compute interest through

DocketMath’s interest calculator lets you plug in these dates so you can see how much interest accrues in each phase.

4. Simple vs. compound interest

Many litigation‑related interest statutes use simple interest (interest only on the principal, not on previously accrued interest). But:

• Some contractual agreements may call for compound interest (e.g., monthly compounding).
• Some judgments may specify a particular method of accrual.

When you calculate interest in Maine, you should:

• Confirm whether the applicable statute calls for simple interest.
• Check whether your contract or judgment explicitly requires compounding, and at what frequency (monthly, annually, etc.).

In DocketMath, you can choose:

• Simple interest – most common in court‑ordered interest
• Compound interest – if your contract or order uses it

This choice can significantly change the final number over long time spans.

5. Variable statutory rates over time

Maine’s statutory interest rate is not always a single, permanent number. It can:

• Change from year to year, or
• Be defined by reference to another indicator (e.g., a federal rate plus a margin).

That leads to two practical questions for your calculations:

1. Which year’s rate applies?
   Often keyed to the year the action is filed or the year of judgment.

2. Do you need to split the timeline?
   For long‑running cases, you may have:

   • One rate for an earlier period, and
   • A different rate after a statutory change.

A robust calculator can help by:

• Allowing you to override the default rate when you know the specific statutory number that applies for that time period.
• Letting you break the calculation into segments (e.g., one calculation per rate period) and then sum the results.

6. Partial payments and changing principal

In real cases, money often moves in pieces:

• The defendant makes a partial payment while the case is pending.
• The judgment is partially satisfied but not fully paid.
• There are costs, fees, or added principal that become interest‑bearing later.

For Maine interest calculations, this means:

• You may need to reduce the principal as each partial payment is applied.
• Interest should accrue on the remaining balance, not the original principal, after each payment.
• The allocation of each payment (principal vs. interest vs. costs) may be governed by:

  • Contract terms,
  • Statute, or
  • Court order.

DocketMath’s calculator is designed so you can:

• Enter multiple principal changes or payments over time.
• See how each payment affects the interest going forward.

Use the calculator

You can model Maine interest scenarios using DocketMath’s interest calculator at /tools/interest. Here’s how to think about the key inputs and how they drive the outputs.

Run the Interest calculation in DocketMath, then save the output so it can be audited later: Open the calculator.

Step 1: Choose the jurisdiction and context

• Jurisdiction: Select Maine (US‑ME) if the interest rule you’re applying is governed by Maine law.
• Context/type (if available in your workflow):

  • Contract claim
  • Judgment
  • Other civil claim

This helps you keep your calculations organized and reminds you which rule you’re applying.

Step 2: Enter principal and dates

Core inputs:

1. Principal amount

   • The dollar amount on which interest should accrue.
   • If you have multiple components (e.g., damages + costs), you can:

     • Run separate calculations for each component, or
     • Combine them only if they share the same interest rule and start date.

2. Interest start date
   Examples:

   • Filing date of the complaint
   • Date of breach
   • Date specified in a contract
   • Date specified in a judgment

3. End date

   • For prejudgment interest: the judgment date.
   • For post‑judgment interest: the payment date or a projection date.

How these affect outputs:

• A longer time span increases the total interest.
• Even small changes in the start date (filing vs. service, invoice vs. breach) can significantly affect the result in high‑value cases.

Step 3: Set the interest rate and method

You’ll typically choose one of two approaches:

1. Use a known statutory or contractual rate

   • Example: “8% per year simple interest.”
   • Enter the rate and select simple interest.

2. Use a custom or variable rate structure

   • If Maine law ties the rate to an external benchmark (e.g., a federal rate plus a margin), or if the rate changed mid‑stream:

     • Break the timeline into segments:

       • Segment 1: Start date → change date, rate A
       • Segment 2: Change date → end date, rate B
     • Run a calculation for each segment and sum the interest.

How rate settings change the outputs:

• Higher rate → more interest for the same time period.
• Compound vs. simple:

  • Simple: Interest grows linearly with time.
  • Compound: Interest grows faster, especially over multi‑year periods.

Step 4: Add partial payments or principal changes (optional)

If your Maine case involves payments over time:

1. Identify each payment date and amount.
2. Decide how to allocate each payment:

   • All to principal
   • Interest first, then principal
   • Another allocation method consistent with your contract or judgment
3. In DocketMath:

   • Record the payment as a principal reduction on the payment date, or
   • Use the payment/allocation features (if available in your workflow).

Effect on outputs:

• Each payment reduces the balance that continues to accrue interest.
• Earlier payments have a larg

Sources and references

Start with the primary authority for Maine and confirm the effective date before relying on any output. If the rule has been amended, update the inputs and rerun the calculation.

• 14 M.R.S. § 1602

Related reading

• Common interest mistakes in Rhode Island

• Worked example: interest in Maine

• Inputs you need for interest in North Carolina

• Why we started the DocketMath blog