Two methods
Simplified: $5 per sq. ft., up to 300 sq. ft. (max $1,500).
Actual: Pro-rata share of eligible costs (rent, utilities, etc.).
Actual: Pro-rata share of eligible costs (rent, utilities, etc.).
Regular & exclusive use
Space is used on a continuing basis and only for business—no personal use.
Principal place of business
Admin/management is primarily done here, even if you also work elsewhere.
Documentation
Keep photos of the space, a simple floor plan, and utility statements.
Switching methods
You can generally choose the method each year; actual may win when costs are high.
Tip
Save a single folder with: floor plan, photos, square footage notes, and two recent utility statements. Future-you will thank you.