The short answer is—there really is no Chapter 20 bankruptcy.  However, a technique has been developed whereby individuals who need the benefits of a Chapter 13, but for some reason (usually their total liabilities are above the debt limits) cannot file a Chapter 13.  Basically this technique involves the filing of a Chapter 7 bankruptcy, which discharges most, if not all, of the obligations.  Then a Chapter 13 bankruptcy is filed to repay the secured creditors, tax obligations, and any nondischargeable debts.  Thus, a Chapter 7 followed by a Chapter 13 is the so-called "Chapter 20" bankruptcy.  Attempting a Chapter 20 can be quite complex and is very risky if not done correctly.  Only an experienced bankruptcy attorney should attempt to use this technique.