The tweet is correct. In fact, page 2 , paragraph 1 of the IRS doc you linked to actually uses some of the same wording as the tweet does: * (1) Former § 174(

The tweet is correct. In fact, page 2 , paragraph 1 of the IRS doc you linked to actually uses some of the same wording as the tweet does: * (1) Former § 174(a)(1) provided that a taxpayer may treat research or experimental expenditures which are paid or incurred by the taxpayer during the taxable year in connection with the taxpayer’s trade or business as expenses which are not chargeable to capital account. The expenditures so treated were allowed as a deduction. * While I would agree that the tweet's wording could have been better - and your quote is clearer - the tweet above is not wrong.