WorkflowLitigation & Dispute Resolution

Prejudgment Interest Calculator

A prejudgment interest calculator that reads the invoices, payments and contract from the record, prices each defensible start date, and cites the source of each rate and date.

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Walk the screens from invoice to signed declaration ↓

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The problem

Interest on a won contract case still gets built in spreadsheet tabs

Liability is decided and the judgment hearing is weeks away. An associate pulls the invoices, the client’s ledger and the remittances, looks up the statute, and builds one spreadsheet tab per invoice. Then the partner asks what the number becomes if the court runs it from the demand letter, and every tab gets rebuilt from scratch.

Nothing in the workbook says which page a due date came from or why a partial payment landed where it did. An invoice footer with shorter terms than the contract, a credit memo the other side claims, or a payment applied oldest-first can each move the figure, and opposing counsel finds the one that was missed.

Built forLitigation partnersLitigation associatesDamages analystsPractice support teams

The Problem Today

Interest turns on the rate rule, the start date and compounding, and every state answers differently.

51: jurisdictions, each with its own interest rule published
$148M: of prejudgment interest carried by one appellate award published

Computed manually at most firms

Invoices
Payments
Statutes
Tabs

A rebuild for each what-ifAnother start date means re-running each tab
No source behind a numberOpposing counsel attacks a figure nobody can trace

The Solution

Read from the recordEach amount, due date and payment cited to its page
Rate rule quotedThe contract’s law clause and the statute, with what each rule is worth
Start dates valuedDate of breach against the demand letter, side by side with authority
Chosen, certified, signedThe partner picks the position; the analyst certifies and signs

Built-in controls

Only a partner chooses the rule and start date
Disputed credits held out until a partner rules
Matter records stay out of model training

What You Get

Firms file a schedule that ties to the ledger to the cent, with the defense’s start date already answered.

≈2 h: of analyst time for a cited schedule, down from about 3 days our estimate

An exhibit by day or by monthThe same schedule by day, by month or by invoice
A declaration that matchesThe brief and the exhibit carry the schedule’s own figures
What-ifs in secondsChange a date or a rule and the totals reflow

From the record to the stand

The prejudgment interest calculator, from invoice page to declaration

Nine screens, in the order a damages workstream runs, each with the job it does and the role it answers to.

01Damage elements and findings
Invoices read from the record, each due date set by the contract
How it works
- All 14 invoices: amount, date and payment term read, each cited to its page
- Due dates come from the contract’s net 45 terms, whatever an invoice footer says
- Unpaid principal of $9,301,472.60 ties to the client ledger
- Findings sit beside the table with their effect on the total
Senior associateNo more retyping fourteen invoices into a spreadsheet and hoping the due dates match the contract before the partner asks where each one came from.
02Source page for one invoice
A source page behind each value, down to the invoice line
How it works
- Invoices, contract clauses, remittances, letters and statutes listed as sources
- The page opens with the value highlighted where it was read
- A side panel shows where the value is used: tape, schedule, declaration
- Values are read from the page; a correction needs a reason and shows in the history
Damages analystWhen opposing counsel attacks a due date, the invoice page behind it opens from the figure itself, not from a search of a shared drive.
03Remittance behind a payment
Payments applied to the invoice each remittance names
How it works
- Two payments, $370,000.00 in all, matched to their invoices
- A remittance that names an invoice is applied to that invoice
- Oldest-first applies only when a payment names no invoice
- Each citation opens the remittance advice it was read from
Damages analystShows which invoice each partial payment reduced, with the remittance behind it, so the principal on each line can be defended.
04Rate rules
A rate rule picker that quotes each statute and prices it on this case
How it works
- Reads the governing-law clause, and all 22 articles for an interest clause
- Each candidate rule shows its rate, its start date and its source text
- The statutory rate of 9.00% simple is worth $2,472,316.59 here
- The forum’s own rule, at an illustrative 7.50%, comes to $1,530,005.87
Litigation partnerSees the rule the contract points to and the one the forum could apply, each with its text and its value, before choosing which to argue.
05Interest calculator
A calculator tape that prints principal, rate and days for each invoice
How it works
- Four dials: accrual start, rate rule, simple or compound, and the through date
- A running total by day, with the other position drawn as a ghost line
- Each tape line cites its invoice page and the contract’s payment term
- Damages with interest of $11,773,789.19 and a per diem of $2,293.51
Senior associateAnswers the partner’s what-if on another start date during the same conversation, and the fourteen tabs never get rebuilt.
06Accrual positions side by side
The defense’s demand-date position priced beside the date of breach
How it works
- Each defensible start date valued on the same 14 invoices
- Moving from the demand letter to the date of breach adds $412,614.13
- A timeline marks due dates, payments, demand, filing and judgment
- Each position carries its authority and the risk a court sees in it
Litigation partnerKnows what each start date is worth and why a court would accept it, so the brief answers the defense’s date before the defense raises it.
07The partner’s choice
The partner’s pick of rule and start date, written down with a reason
How it works
- Rate rule, position, interest and fallback on one panel
- The reason is written for the record, citing the clause and the statute
- The associate who prepared the inputs cannot approve them
- The intermediate date stays ready as the court’s alternative
Litigation partnerPuts her call and its reasoning in the file, so nobody later has to reconstruct why the motion ran interest from each due date.
08Schedule and tie-out
A schedule by day that ties to the client ledger to the cent
How it works
- One engine shows the schedule by month, by day or by invoice
- Unpaid principal, payments and invoiced totals each tie to the record
- 61 of 61 rates and dates cited before she certifies
- Certifying locks version 7; a change makes version 8 and needs a new certificate
Damages analystCertifies a schedule she can defend line by line on the stand, without re-running the tabs after each late change to an input.
09Signed declaration
A damages declaration drafted from the schedule, its figures cited
How it works
- Drafted from the certified schedule, with exhibits A to C
- 18 of 18 figures cited and matched to the schedule to the cent
- Checks before filing: the partner’s choice, the certificate, the signature
- The analyst signs it herself; agents only draft
Damages analystSigns a declaration whose numbers match the brief and the exhibit, because no figure is retyped between the three.

Around the schedule

What-ifs, exhibits and history around the prejudgment interest calculator

More screens the team opens on the same matter.

Interest calculator set to the date of written demand: $2,059,702.46, down $412,614.13 against the date of breach, with the tape recomputed — **The demand date, dialed in**Turn the accrual dial to the demand letter and the total drops to $2,059,702.46, shown as −$412,614.13 against the date of breach.

Ladder of five accrual positions as bars on one scale, from $2,472,316.59 down to $1,530,005.87, each with its authority and its risk — **Five positions on one scale**Date of breach, intermediate date, demand, filing and the forum’s rule, each with its authority, its risk and its distance from position A.

Damages schedule by month: invoices accruing, principal accruing, interest that month and running total, with the ledger tie-out beside it — **The exhibit, by month**62 months from the first due date to judgment, with interest per month and a running total. The sum of months equals the sum of invoices.

Draft damages section of the brief asking for $11,773,789.19 plus a per diem, with its statutes, clauses and declaration paragraphs cited inline — **The brief’s damages section**Drafted from the same schedule: judgment of $11,773,789.19 plus $2,293.51 a day, and an answer to the demand-date argument.

History of input changes: the net 45 correction, the switch to the date of breach, the partner’s choice and the signature, each with its effect — **Who changed what**Each input change with who made it, from what to what, why, and its effect on interest. Agents and people sit on one record.

Settings with the firm’s rate tables by jurisdiction, the day count and rounding rules, and a roles grid that separates prepare, certify and choose — **Rate tables the firm keeps**Rate, basis, start rule and source for each jurisdiction in the firm’s table of 51, with day count, rounding and who may do what.

Five start dates on the same invoices, and $942,310.72 between them

Interest through judgment on the fourteen unpaid invoices, at the statutory rate unless noted. The forum’s rate is illustrative.

Accrual position	Interest ($)	Against date of breach
A · Date of breach: each invoice from its due date	2,472,316.59	Proposed and chosen
B · One reasonable intermediate date	2,463,233.82	−9,082.77
C · Date of written demand	2,059,702.46	−412,614.13
D · Date suit was filed	1,836,007.06	−636,309.53
E · The forum’s own rule, 7.50% from filing	1,530,005.87	−942,310.72
Position A compounded yearly	2,727,093.35	Reference only: the rule requires simple interest

A claimed credit, a net 30 footer, a named payment and no rate clause

Four things the agents found while reading this record, each shown with its effect and the person who settles it.

A credit memo the defendant claims

A $38,500.00 fuel-surcharge credit against one invoice, marked disputed and never issued in the client’s ledger. Netting it would cut interest by $10,632.33, so it stays out until the partner decides.

An invoice footer that says net 30

The contract says net 45 and governs. Its later due date is the safer figure; net 30 would have added $1,773.26. The analyst confirmed it.

A payment that names its invoice

The $250,000 remittance names the invoice it pays, so it is applied there. The contract’s oldest-first rule reaches only payments that name no invoice.

No interest clause in 22 articles

All 22 articles were read and none sets a rate for late payment, so the statute supplies it, quoted beside the governing-law clause that points to it.

Five calls on the interest figure that stay with the partner and analyst

Agents read, apply, compute and draft. The attorney makes these calls.

Which rate rule governsThe rule finder quotes the governing-law clause and each statute that could apply. The partner chooses, with a reason on the record.

Which accrual date to argueEach date is valued with its authority and its risk. The valuer takes no position for the client.

Whether to net a disputed creditA credit the client’s ledger disputes stays out of the schedule until a partner decides.

Certifying the scheduleThe analyst certifies. The associate who prepared an input cannot approve it.

Signing and filingAgents draft the declaration and the damages section. They do not sign, file, or contact opposing counsel or the court.

Rates, start dates and certified schedules, answered

What is a prejudgment interest calculator?

A prejudgment interest calculator works out the interest owed on damages from the day it starts to run until judgment. This one reads the invoices, payments and contract from the record, quotes the rate rule, computes each invoice by day to the cent, and cites the source of each rate and date.

Can it run interest from each due date and from one intermediate date?

Yes. It values each defensible start date on the same invoices: each item from its due date, one reasonable intermediate date, the demand letter, the filing date and the forum’s own rule. The partner chooses, and the fallback goes into the declaration as its own exhibit.

Is prejudgment interest simple or compound here?

It follows the rule. The basis dial switches between simple and yearly compounding, and when the governing rule requires simple interest, the compound figure is shown for reference and kept out of the schedule.

How does it decide which statute sets the rate?

It does not decide. The rule finder reads the governing-law clause and each article for an interest clause, then quotes each statute that could apply with its rate, its start rule and its value in the case. The partner records the choice with a reason.

What happens to a credit memo the other side claims?

Payments are applied as each remittance names them. A credit the client’s ledger marks as disputed is held out, with its effect on principal and interest shown beside it, until a partner decides.

Who can change an input after the schedule is certified?

A change makes a new version that needs a new certificate. The history records who changed what, from what to what, why, and its effect on the interest.

Is the arithmetic done by a language model?

No. The interest engine is code: the same inputs give the same cents. Each invoice is rounded to the cent and then summed, on actual days over the year length the contract sets.

Litigation & Dispute Resolution

Price every start date
before the defense names one.

We’ll take the invoices, ledger and contract from a case you have closed and build its cited schedule with you.

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Prejudgment Interest Calculator

Interest on a won contract case still gets built in spreadsheet tabs

The Problem Today

The Solution

What You Get

The prejudgment interest calculator, from invoice page to declaration

Invoices read from the record, each due date set by the contract

A source page behind each value, down to the invoice line

Payments applied to the invoice each remittance names

A rate rule picker that quotes each statute and prices it on this case

A calculator tape that prints principal, rate and days for each invoice

The defense’s demand-date position priced beside the date of breach

The partner’s pick of rule and start date, written down with a reason

A schedule by day that ties to the client ledger to the cent

A damages declaration drafted from the schedule, its figures cited