Commuting to USA?

Regular commuters from Canada or Mexico: 
​For the Substantial Presence Test do not count the days on which you commute to work in the United States from your residence in Canada or Mexico if you regularly commute from Canada or Mexico. You are considered to commute regularly if you commute to work in the United States on more than 75% of the workdays during your working period. ​ 

For this purpose, “commute” means to travel to work and return to your residence within a 24-hour period. “Workdays” are the days on which you work in the United States or Canada or Mexico. “Working period” means the period beginning with the first day in the current year on which you are physically present in the United States to work and ending on the last day in the current year on which you are physically present in the United States to work. If your work requires you to be present in the United States only on a seasonal or cyclical basis, your working period begins on the first day of the season or cycle on which you are present in the United States to work and ends on the last day of the season or cycle on which you are present in the United States to work. You can have more than one working period in a calendar year, and your working period can begin in one calendar year and end in the following calendar year.

Example. Maria Perez lives in Mexico and works for Compañía ABC in its office in Mexico. She was assigned to her firm's office in the United States from February 1 through June 1. On June 2, she resumed her employment in Mexico. On 69 days, Maria commuted each morning from her home in Mexico to work in Compa- ñía ABC's U.S. office. She returned to her home in Mexico on each of those evenings. On 7 days, she worked in her firm's Mexico office. For purposes of the substantial presence test, Maria does not count the days she commuted to work in the United States because those days equal more than 75% of the workdays during the working period (69 workdays in the United States divided by 76 workdays in the working period equals 90.8%).