What business expenses can Substack writers deduct?

Substack writers can deduct ordinary and necessary business expenses — costs that are both common in the writing trade and directly useful for operating the newsletter. The IRS standard from Publication 334 requires that expenses be both ordinary (common and accepted in the trade) and necessary (helpful and appropriate for the business). Personal expenses that overlap with newsletter work require allocation.

Deductible expenses typically include: writing and publishing software tools (grammar checkers, design tools, email marketing add-ons); research subscriptions that directly support the newsletter's content; professional development costs like courses, books, and conferences on writing or the newsletter's subject matter; contractor fees paid to editors, designers, or illustrators; and business-related phone and internet costs allocated to business use. Writers who pay other contributors or guest writers must issue 1099-NEC forms to US-based contractors who are paid $600 or more during the year.

A dedicated home office space that is used regularly and exclusively for newsletter work qualifies for the home office deduction under IRS Publication 587. Writers can use the simplified method ($5 per square foot, up to 300 square feet) or the regular method (actual home expenses multiplied by the percentage of the home used for business). Spaces used for both personal and business purposes — a kitchen table where the writer also eats meals — do not meet the exclusive-use test and do not qualify.

This is general tax information, not tax advice. Your situation may differ; consult a licensed CPA before making tax decisions.