<prompt> Translate the following text to EnglishMsaada wa kodi usioweza kurudishwa huenda usiwe na ufanisi wa kuhimiza akiba ya walipa kodi wenye mapato ya chini, ambao tayari wanadaiwa kodi ndogo ya mapato ya shirikisho au hawana.  <response>: Nonrefundable tax incentives may not be particularly effective in encouraging saving by lower-income taxpayers, who already owe relatively little or no federal income taxes. 