Labour markets for personal and household services (PHS) are rife with informal employment. Some policies aim to combat informality in PHS with subsidized service vouchers, but their effects are poorly documented. This contribution evaluates the Belgian service vouchers (1) documenting their formalization effectiveness, and (2) accounting for the persistence of informal employment. To this end, we exploit several types of data and methods. A first analysis, based on Eurobarometer data, brings in evidence that informal PHS purchased were approximately halved under the policy introduced in 2001. Second, a discrete choice experiment shows that households prefer formal employment, including those that currently employ informally. Third, a survey in the Brussels metropolitan area shows that the persistence of informal employment lies in the relationship of informal employers with their domestic, from whom they are not willing to part. They nevertheless intend to switch to formal employment in the case of turnover. One thus expects partially delayed effects of formalization policies in general, and of the service voucher system in particular. Overall, these results are in line with Portes' claim that informality is facilitated by strong social relationships, and by differences in price and transaction costs.