tax morale more salient through careful messaging, with mixed results. Kettle et al. (2016) finds that both letters emphasizing national pride and those emphasizing social norms improve compliance in Guatemala, but not significantly more than a letter invoking a heightened probability of audit. In richer countries, randomized studies of letter or e-mail campaigns typically find that attempts to emphasize the social contract or civic duty either have little impact or are marginally effective (Coleman 1996; Blumenthal et al. 2001; Torgler 2004; Ariel 2012; Fellner et al. 2013; Castro and Scartascini 2015; Meiselman 2018) with some exceptions (Hallsworth et al. 2017). Krause (2020) finds that messages that emphasize the social pressure mechanism in Haiti might even have a negative effect on tax compliance. This is consistent with results from psychology research which have shown that in contexts with low rates of pro-social coordination, a mechanism known as antisocial punishment could be at play (Herrmann et al. 2008).

A recent meta-analysis (Antinyan and Asatryan 2020) of studies of nudges for tax compliance finds that deterrence nudges are on average more effective than tax morale nudges. The metaanalysis also finds that nudges seem to work better for the sub-samples of late payers, which is the sample we focus on in this paper.

# **3 Experiment and data collection**

## **3.1 Baseline data and randomization**

The frame for this experiment is a list of 241,200 properties for which, as of June 1, 2018, no property tax had been paid to the TRA for the 2017/2018 tax year. The deadline for property tax payments to be completed was June 30th. After June 30 had passed, the TRA extended the deadline for another two weeks, although continued to accept payments after this point.

As some taxpayers own multiple parcels, we collapsed these data to the taxpayer level (237,699 taxpayers), as indicated by the taxpayer identification number associated with the property. We use two sources of information in the randomization: the location of the property and whether or not the property had been served a ‘demand notice’ at the time the data was collected. The location of the property is the lowest level of administration in Dar es Salaam, the sub-ward or ‘mtaa’ level. We assign taxpayers the same location as their property. When taxpayers have multiple properties that span more than one sub-ward, we pick the modal subward. Where there is no modal sub-ward, we randomly choose one of those sub-wards to assign to the taxpayer. Ultimately, the randomization was conducted within 1,211 different strata, which were defined both by the location of the property (sub-ward) and whether a bill had been issued.

Demand notices are bills issued by the TRA to landowners. Approximately 19 percent of the experimental sample had been issued a bill at the time of the data collection. The TRA issued bills (called “demand notices”) in bulk for a specific area of the city (this could be a ward or a set of core streets) and sent them to landowners by manual delivery by TRA officers and temporary interns, typically after seeking the support of street leaders. While the goal is to cover all areas of the city every fiscal year, limited financial and human resources explain why only a subset of the city is covered in practice.

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