The regular withholding rate is the rate specified in the IRS tax tables or rates published in tax treaties. Withholding at an adjusted amount refers to withholding at a rate different from the regular rate due to a tax treaty provision or a request from the payee. For example, a tax treaty may provide for a reduced rate of withholding on certain types of income. In such cases, the payer must withhold at the adjusted rate and report it on Form 8288. Another situation where withholding at an adjusted amount may apply is when the payee requests a lower rate of withholding based on their income and tax filing status. The payer must obtain a valid withholding certificate, such as Form W-8BEN or W-8BEN-E, from the payee before withholding at the adjusted rate. The payer must then report the adjusted rate on Form 8288.