How do I find information for Form 3510 line 15a

This may be a California form. Credit for Prior Year Alternative Minimum Tax — Individuals or Fiduciaries

• An unused California Alternative Minimum Tax credit carryover from the previous year may not offset the AMT calculated on California Schedule P.
• You can get the Instructions for Form FTB 3510
• If you have additional questions I suggest you contact the   California DOR