IRS 90 Day Mileage Rule

[Max W]

Recently, I've come across some article about the 90 day mileage rule, but none of them spells out the number of the IRS Reg. that provides this.  There is also a First-week-of-the month rule.  Can anyone state the Reg. and does it apply to both expense methods.

[jklcpa]

Reg sec 1.274-5T(c)(3)(ii)(A) and reg sec 1.274-5T(c)(3)(ii)(C) Example 1

https://www.law.cornell.edu/cfr/text/26/1.274-5T

Good info here with the cites at bottom: https://bradfordtaxinstitute.com/Content/IRS-Mileage-Log.aspx

[Max W]

Thanks, Judy.  That was very helpful.