Per the IRS Instructions for Form 4684 Casualties and Thefts, page 6:

Losses From Ponzi-Type Investment Schemes

The IRS has issued the following guidance to assist taxpayers who are victims of losses from Ponzi-type investment schemes.

• Revenue Ruling 2009-9, 2009-14 I.R.B. 735 (available at https://www.irs.gov/pub/irs-drop/rr-09-09.pdf) 
• Revenue Procedure 2009-20, 2009-14 I.R.B. 749 (available at https://www.irs.gov/pub/irs-drop/rp-09-20.pdf)
• Revenue Procedure 2011-58, 2011-50 I.R.B. 849 (available at https://www.irs.gov/irb/2011-50_IRB#RP-2011-58)

If you qualify to use Revenue Procedure 2009-20, as modified by Revenue Procedure 2011-58, and choose to follow the procedures in the guidance, first fill out Section C to determine the amount to enter on Section B, line 28. Skip lines 19 to 27. Section C of Form 4684 replaces Appendix A in Revenue Procedure 2009-20. You don't need to complete Appendix A.

For more information, see the instructions for Section C later and the above revenue ruling and revenue procedures.

If you choose not to use the procedures in Revenue Procedure 2009-20, you may claim your theft loss by filling out Section B, lines 19 to 39, as appropriate.

To enter these losses in TaxAct®:

1. From within your TaxAct return (Online or Desktop), click Federal. On smaller devices, click the menu icon in the upper left-hand corner, then select Federal 
2. Click Itemized or Standard Deductions in the Federal Quick Q&A Topics menu to expand the category and then click Safe harbor treatment from a Ponzi Scheme
3. Click +Add Form 4684 Section B to create a new copy of the form or click Review to review a form already created 
4. The program will proceed with the interview questions for you to enter or review the appropriate information