List each trip with dates and purpose, show it was for the same corporate group, and subtract the days from the year abroad. The trips do not break continuity but cannot be counted toward the year.
Disclose the trips and let the arithmetic show the year
The regulation provides that time spent in the United States in lawful status for a related company, and brief business trips, are not interruptive of the continuous year abroad but are not counted toward it. The petition should therefore include a simple table: departure date, return date, purpose, immigration status used for each visit. Support it with travel records and the employer's assignment letters.
Then present the abroad total with those days removed. Omitting the trips is the error to avoid; entry records exist and an adjudicator who finds undisclosed U.S. work will question every other date in the file.
If the trips were long enough that the year abroad is not yet complete, the petition should wait. Where the visits involved productive work at the U.S. site, confirm the status used was appropriate, because that is a separate question from the L-1A calculation and can surface at the interview or port of entry.