The Marking Date and the Damages Window

Question 79: The Marking Date and the Damages Window

Your role

You represent NovaTag, the owner of a product patent asserted against DeltaMark's Model K. Determine the first recoverable damages date under the supplied marking and actual-notice rules and calculate the royalty window through patent expiration.

Governing law

Assume the following patent-damages rules apply:

1. A patentee that makes or sells a patented article must give constructive notice by marking substantially all patented articles. Before substantial compliance, damages are unavailable unless the accused infringer receives actual notice.

2. For this assignment, marking at least 95 percent of distributed patented units constitutes substantial compliance. A lower percentage does not.

3. Constructive notice begins on the date substantial compliance begins and continues while compliance remains at or above 95 percent.

4. Actual notice requires an affirmative communication identifying the patent, identifying the accused product or conduct, and charging infringement. General awareness, a licensing invitation, or a statement that products use similar technology is insufficient.

5. Once constructive or actual notice begins, damages may be recovered for later infringement through patent expiration, subject to the filing lookback.

6. A civil action may recover no damages for infringement more than six years before filing. The lookback does not shorten a later notice-based start date.

7. The patent owner bears the burden of proving marking compliance or actual notice. The accused infringer bears the burden of proving any earlier unmarked patented sales after the patentee establishes a compliant program.

8. Use calendar months for the supplied unit and royalty calculation. Each listed month contains 2,000 infringing units, and the reasonable royalty is $18 per unit.

Facts

NovaTag's patent issued January 1, 2022 and expired December 31, 2025. NovaTag sold a patented tracking tag throughout that period.

Its marking records show:

• January 1 through June 30, 2022: 60 percent of distributed units bore the patent number.
• Beginning July 1, 2022: 97 percent bore the patent number.
• Compliance remained at 97 percent or higher through expiration.

DeltaMark sold 2,000 Model K units in every calendar month from March 2022 through December 2025.

On October 15, 2022, NovaTag emailed DeltaMark:

“We believe Model K uses technology similar to ours. We are interested in discussing a commercial license.”

The email did not identify a patent number and did not state that DeltaMark infringed.

On February 1, 2023, NovaTag sent a letter identifying the patent, identifying Model K, mapping two claims to Model K, and stating that DeltaMark's sales infringed. DeltaMark received it that day.

NovaTag filed suit on June 1, 2026. The parties stipulate for this assignment that every Model K unit in the recoverable period infringed and that $18 per unit is the proper royalty. Ignore interest and enhanced damages.

Assignment

Analyze and calculate:

• Whether the January through June 2022 marking rate gave constructive notice.
• The first constructive-notice date.
• Whether the October 15 email gave actual notice.
• The effect of the February 1 letter.
• The six-year filing lookback.
• The first recoverable damages date.
• The number of recoverable calendar months and units through expiration.
• Total royalty damages.
• The damages amount that would result if February 1, 2023 were incorrectly used as the start date.
• The value lost from that incorrect start date and the unrecoverable March through June 2022 period.

Q79 key (Patent Marking Window)

1. The 60 percent rate through June 30, 2022 is below the supplied 95 percent threshold, so it gives no constructive notice. Missed: damages begin at patent issuance despite deficient marking.
2. Constructive notice begins July 1, 2022, when marking reached 97 percent and remained compliant. That date controls because it precedes valid actual notice. Missed: the later demand letter shortens the damages window.
3. The October 15 email is not actual notice because it identifies neither the patent nor an infringement charge. The February 1, 2023 letter is valid actual notice but adds nothing after constructive notice already began. Missed: a licensing invitation is treated as a charge or the valid letter is ignored entirely.
4. Suit on June 1, 2026 has a six-year lookback to June 1, 2020, earlier than all infringement and notice dates, so the lookback does not truncate recovery. Missed: six years is counted from patent issuance or used to recover pre-notice sales.
5. Recoverable period is July 2022 through December 2025: 6 months in 2022 plus 12 each in 2023, 2024, and 2025, totaling 42 months. At 2,000 units per month, recoverable units are 84,000. Damages are 84,000 times $18, or $1,512,000. Missed: month count or unit rate produces a material valuation error.
6. Using February 1, 2023 incorrectly yields 35 months, 70,000 units, and $1,260,000. The lost value would be $252,000, representing July 2022 through January 2023, seven months and 14,000 units. Missed: NovaTag leaves a quarter-million-dollar marked-sales period unclaimed.
7. March through June 2022 contains four months, 8,000 units, and $144,000 in otherwise stipulated royalties that remain unrecoverable because neither marking nor actual notice existed. Missed: the key distinguishes money lost by deficient marking from money lost by choosing the wrong later start date.