The rate of informal firms is high inSub-Saharan Africa, especially for those that arewomen-owned and in the poorest countries, despite a total of107 business regulatory reforms recorded by Doing Businessacross 40 economies in the region. Through an experiment inMalawi, we established an effective and replicable design tooffer informal firms support to formalize, costing much lessthan the typical private sector development intervention.The study shows that one of the primary barriers toregistration for women-owned firms is transaction costs.When registration is madevirtually costless, an overwhelmingnumber of women-owned firms (73 percent) choose to register.However, when offered the chance to engage in costlessregistration for taxes, almost no firms select to pursuethis opt ion. Combining business registration with aninformation session at a bank including the offer of abusiness bank account leads to an increased use of formalfinancial services, and results in increases in women ownedfirms sales and profits of 28 percent and 20 percentrespectively. On the other hand, business registration onits own is not as effective in improving access to financialservices and does not result in enhanced sales and profits.