To improve health coverage and revenue collection, several African countries consider tax-for-health-services programs where informal workers pay income tax for health insurance. We examine these programs in Nigeria, investigating whether informal workers support such initiatives, what parameters improve program perception, and what drives preferences about these parameters. Using a conjoint survey experiment with 12,000 informal workers across 12 Nigerian states, we find citizens more likely to support earmarked tax allocation programs, with tax level being most important. Informal workers with less healthcare experience and need, and those feeling distant from government, prioritize tax level and starting date more than others. Our study shows that informal workers in Nigeria generally support earmarked tax-for-health-services programs, but specific design parameters matter. Preferences vary based on healthcare experience and government trust. These findings inform the design of earmarked tax programs to improve healthcare coverage and revenue collection.