@Anonymous_ is correct. Per IRS Publication 538, dividends become taxable when the taxpayer has "constructive receipt" of the funds. An individual is considered to be in "constructive receipt" of income when the income is credited to his account or made available to him without restriction.
https://www.irs.gov/pub/irs-pdf/p538.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
