In a trademark opposition asserting Section 2(d) based on priority in the use of a trademark, the Opposer must show by a preponderance of the evidence that the Applicant's use of its mark is likely to cause confusion. Major League Baseball Players Ass'n v. Chisena, No. 91240180, 2023 WL 2986321, at *4 (TTAB 2023) (“For purposes of priority, proprietary rights may arise from a prior registration, prior trademark or service mark use, prior use as a trade name, prior use analogous to trademark or service mark use, or any other use sufficient to establish proprietary rights.” (internal quotation and citations omitted)), aff'd, 2026 WL 60319 (Fed. Cir. Jan. 8, 2026); Sage Therapeutics, Inc. v. Sageforth Psych. Servs., LLC, No. 91270181, 2024 WL 1638376 (TTAB 2024); see also Cielo e Terra, S.P.A. v. Hoteles y Viñedos del Valle de Guadalupe S.A. de C.V., No. 91287216, 2026 WL 2624328 (TTAB 2026). See also Herbko Int'l, Inc. v. Kappa Books, Inc., 308 F.3d 1156, 1162 (Fed. Cir. 2002). To establish priority, one must establish that its claimed mark, or a legal equivalent, is inherently distinctive, or that it acquired distinctiveness before the other party's date of first use. See, e.g., Shenzhen IVPS Tech. Co. v. Fancy Pants Prods., LLC, No. 91263919, 2022 WL 16646840, at *16 n.51 (TTAB 2022). 

In considering evidence of prior use for priority, rather than considering individual portions in isolation, one “must 'look at the evidence as a whole, as if each piece of evidence were part of a puzzle which, when fitted together, establishes prior use.'” Kemi Organics, LLC v. Gupta, No. 92065613, 2018 WL 2230555, at *5 (TTAB 2018) (quoting W. Fla. Seafood Inc. v. Jet Rests. Inc., 31 F.3d 1122, 1125-26 (Fed. Cir. 1994) (finding priority of use of a mark for restaurant services on the basis of three advertisements in local newspapers, a Florida state service mark registration, three regulatory licenses, and a food service inspection report)). 

The doctrine of “tacking” allows a party to “clothe a new mark with the priority of an older mark” when “the original and revised marks are ‘legal equivalents' in that they create the same continuing commercial impression.” Hana Fin., Inc. v. Hana Bank, 574 U.S. 418, 419-20 (2015) (“Hana Bank”). Tacking is typically invoked as an affirmative defense or counterclaim that the defendant has priority over the plaintiff because the defendant can tack prior use of another mark onto the use of its current mark. See, e.g., Hana Bank, 574 U.S. at 421; Anthony's Pizza & Pasta Int'l, Inc. v. Anthony's Pizza Holding Co., No. 91171509, 2009 WL 4075365, at *5 (TTAB 2009). But tacking may also be invoked by a plaintiff. See, e.g., Jimlar Corp. v. Army & Air Force Exch. Serv., No. 83984, 1992 WL 280636, at *6 (TTAB 1992). Tacking, however, does not contemplate the merger of two or more distinct prior marks into a later single mark. Hana Bank, 574 U.S. at 419-20; see also Paris Glove of Can., Ltd v. SBC/Sporto Corp., No. 92044132, 2007 WL 2422997 (TTAB 2007) (discussing whether there was a later “material alteration” of the registered mark including whether “the commercial impression of the mark is dependent upon the literal terms” or on "particular stylizations"). 

“The standard for a trademark owner to invoke tacking is strict,” and requires “showing more than a likelihood of confusion between the two marks.” Bertini v. Apple Inc., 63 F.4th 1373, 1377 (Fed. Cir. 2023) (citation omitted). Moreover, a “trademark owner must show tacking is available for each good or service for which it claims priority on that ground,” id. at 1379 (citation omitted), and that “the goods or services must be substantially identical for tacking to apply.” Id. at 1381. Within the normal evolution of goods or services, whether goods and services are substantially identical may depend, "at least in part, on whether consumers would generally expect the new goods or services to emanate from the same source as the previous goods or services." Bertini, 63 F.4th at 1381 ("Nothing in the record supports a finding that consumers would think Apple's live musical performances are within the normal product evolution of Apple Corps' gramophone record."); Wiss & Sons Co. v. W. E. Bassett Co., 462 F.2d 567, 569–70 (CCPA 1972) (determining that a trademark applicant could not tack its use of TRIMLINE for hair cutting shears onto its prior use of QUICK-TRIM for grass shears because hair cutting shears are not in the normal expansion from grass shears); see also FVDED, LLC v. Faded Culture Studio, LLC, Opposition No. 91286343 (TTAB Nov. 2, 2026) ("By definition, clothing and barbering services are not 'substantially identical' and thus the use of any prior mark for clothing per se cannot be tacked onto Opposer's current use of FADED CULTURE for barbering services to establish priority of use of FADED CULTURE for those services."). 

In Humble Oil & Refin. Co. v. Sekisui Chem. Co. of Japan, No. 42401, 1970 WL 9925 (TTAB 1970), where the goods were unchanged, the issue was whether ESLON was “a mere modification of its trademark ‘S-LON' or ‘S'-LON' which has been used in commerce by [the applicant] from a date prior to the date of first use by [the opposer] of the registered mark ‘ESCON.'” Humble Oil, 1970 WL 9925, at *2. The Board ultimately “conclude[d] that ‘S-LON' and ‘ESLON' are legal equivalents” (which differed "essentially only by one letter and a hyphen" and would have been "recognized as the same mark") such that the applicant could rely on its prior use of S-LON in the United States. Id. at *10. In essence, the Board in Humble allowed the applicant to tack its prior use of S-LON onto its use of ESLON for purposes of establishing its priority and applied the doctrine of tacking without expressly saying so. FVDED, LLC v. Faded Culture Studio, LLC, Opposition No. 91286343 (TTAB Nov. 2, 2026) (distinguishing the Opposer's reliance on Humble in unsuccessful argument that tacking is unnecessary where there are only minor stylistic variations in presentation of a trademark). The TTABlog commented that FVDED was a "thorough and instructive opinion."  

Furthermore, belatedly claiming a date of first use earlier than the date claimed in its application carries risk in litigation because “[w]hen a party claims a date earlier than the date it alleged when it filed its application, that is considered a change in position, contrary to the admission it made against interest at the time it filed the application; in these circumstances, its proof of the earlier date must be clear and convincing.” JNF LLC v. Harwood Int'l Inc., No. 92070634, 2022 WL 4379238, at *4 (TTAB 2022) (citing Hydro-Dynamics, Inc. v. George Putnam & Co., 811 F.2d 1470, 1473 (Fed. Cir. 1987)). “This enhanced burden of proof can apply to either party in an inter partes proceeding, plaintiff or defendant.” Id. (citation omitted).