https://www.irs.gov/pub/irs-drop/rr-99-7.pdf
HOLDING
In general, daily transportation expenses incurred in going between a taxpayer’s residence and a work location are nondeductible commuting expenses. However, such expenses are deductible under the circumstances described in paragraph (1), (2), or (3) below
(3) If a taxpayer’s residence is the taxpayer’s principal place of business within the meaning of § 280A(c)(1)(A),
the taxpayer may deduct daily transportation expenses incurred in going
between the residence and another work location in the same trade or
business, regardless of whether the other work location is regular or
temporary and regardless of the distance.
§280(c)(1)(A): "
the term “principal place of business” includes a place of business
which is used by the taxpayer for the administrative or management
activities of any trade or business of the taxpayer if there is no other
fixed location of such trade or business where the taxpayer conducts
substantial administrative or management activities of such trade or
business."
