Do I have to report how I spend my surplus funds?

Yes.

• A candidate who does not open or move surplus funds to a surplus funds account continues to file C-4 reports to disclose surplus fund spending. These C-4 reports are filed monthly or, if spending is sporadic, file the C-4 whenever more than $200 has been spent since the last C-4 report was filed.
• A candidate who opens a surplus account registers the account. Use the campaign committee name + "surplus funds" for the name of the committee. File monthly C-4 reports showing expenditures. At the end of each month, if you have not spent $200 since the last surplus funds account C-4 report was filed, you may wait until you do and then file a report for multiple months. Note: Money transferred to a surplus funds account should be reported by the campaign as an expenditure.