0000063075 2012-06-28 2012-06-28 0000063075 ck0000063075:S000002496Member ck0000063075:C000092113Member 2012-06-28 2012-06-28 0000063075 ck0000063075:S000002496Member ck0000063075:C000006759Member 2012-06-28 2012-06-28 0000063075 ck0000063075:S000002496Member ck0000063075:C000006758Member 2012-06-28 2012-06-28 0000063075 ck0000063075:S000002496Member ck0000063075:C000006757Member 2012-06-28 2012-06-28 0000063075 ck0000063075:P0001-S000002496Member ck0000063075:S000002496Member 2012-06-28 2012-06-28 Other 2012-06-28 MFS SERIES TRUST IX /MA/ 0000063075 false 2012-06-28 2012-06-28 2011-08-28 MFS Municipal Limited Maturity Fund <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">SUPPLEMENT TO PROSPECTUS <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">The date of this supplement is June 28, 2012 <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">  <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">Certain MFS® Funds <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;line-height: normal;text-autospace:none">  <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;line-height: normal;text-autospace:none">  <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;line-height: normal;text-autospace:none">Effective immediately, the footnote (#) directly beneath the first table in the sub-section entitled “Fees and Expenses” under the main heading “Summary of Key Information” is restated in its entirety as follows: <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">  <table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" style='border-collapse:collapse'> <tr> <td width="25" valign="top" style='width:19.0pt;padding:0in 0in 0in 0in'> <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.8pt;margin-bottom: 0in;margin-left:0in;margin-bottom:.0001pt;line-height:normal;text-autospace: none"># </td> <td width="743" valign="top" style='width:557.0pt;padding:0in 0in 0in 0in'> <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.8pt;margin-bottom: 0in;margin-left:0in;margin-bottom:.0001pt;line-height:normal;text-autospace: none">On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012. </td> </tr> </table>   MTLFX MTLBX MTLCX MTLIX