**Table 3: Impact of message assignment on payment rates**

||**IT**|**T estimat**|**es**|**2S**|**LS estima**|**tes**|
|---|---|---|---|---|---|---|
||Start of<br>experiment|First tax<br>deadline|One month<br>after frst<br>deadline|Start of<br>experiment|First tax<br>deadline|One month<br>after frst<br>deadline|
|**Pooled treatment arms**|||||||
|Treated|-0.000578<br>(-1.04)|0.0147<sup>_∗∗∗_</sup><br>(8.60)|0.0179<sup>_∗∗∗_</sup><br>(8.72)|-0.000663<br>(-1.07)|0.0169<sup>_∗∗∗_</sup><br>(8.88)|0.0205<sup>_∗∗∗_</sup><br>(8.96)|
|**Separate treatment arms**|||||||
|T1: Reminder|-0.000738|0.0153<sup>_∗∗∗_</sup>|0.0177<sup>_∗∗∗_</sup>|-0.000830|0.0173<sup>_∗∗∗_</sup>|0.0199<sup>_∗∗∗_</sup>|
||(0.000605)|(0.00190)|(0.00227)|(0.000681)|(0.00214)|(0.00256)|
|T2: Reciprocity|-0.000601|0.0180<sup>_∗∗∗_</sup>|0.0220<sup>_∗∗∗_</sup>|-0.000638|0.0191<sup>_∗∗∗_</sup>|0.0232<sup>_∗∗∗_</sup>|
||(0.000699)|(0.00224)|(0.00267)|(0.000740)|(0.00237)|(0.00283)|
|T3: Social pressure|-0.000234|0.0101<sup>_∗∗∗_</sup>|0.0144<sup>_∗∗∗_</sup>|-0.000264|0.0117<sup>_∗∗∗_</sup>|0.0167<sup>_∗∗∗_</sup>|
||(0.000707)|(0.00219)|(0.00263)|(0.000850)|(0.00263)|(0.00317)|
|Constant|0.00735<sup>_∗∗∗_</sup>|0.0716<sup>_∗∗∗_</sup>|0.109<sup>_∗∗∗_</sup>||||
||(0.000503)|(0.00150)|(0.00182)||||
|Control mean|0.007|0.072|0.109|0.007|0.072|0.109|
|First stage f-stat||||135,432|135,432|135,432|
|R<sup>2</sup>|0.013|0.041|0.048|0.000|0.001|0.001|
|Obs|143,425|143,425|143,425|143,425|143,425|143,425|
|Test: T1 = T2|0.816|0.181|0.070|0.766|0.418|0.210|
|Test: T1 = T3|0.401|0.008|0.156|0.428|0.016|0.254|
|Test: T2 = T3|0.597|0.001|0.005|0.650|0.007|0.047|

**Notes:** Outcome is the probability a taxpayer made any payment to the TRA by the date indicated. ITT estimates indicate impact of being assigned to treatment. 2SLS estimates instrument the receipt of each message type with assignment to treatment. Robust standard-errors in parentheses. + _p <_ 0 _._ 10 _,∗ p <_ 0 _._ 05 _,∗∗ p <_ 0 _._ 01 _,_<sup>_∗∗∗_</sup> _p <_ 0 _._ 001

control mean of approximately 3,544 TSh, an increase in about 15 percent. Those receiving the reciprocity message gave substantially more: nearly 700 TSh. This is significantly greater than reminder messages, although not significantly greater than social pressure messages at conventional levels of inference.

In Table 5 we use our subsample of taxpayers for whom we have bill data to unpack what proportion of their final tax bill has been paid. Column (1) replicates column (6) of Table 3, then column (2) restricts the sample to the bill subsample, showing that the effect sizes are similar across the two samples. Columns (3) investigates the impact of the three treatments on the proportion of the total tax bill (the 2017/18 bill and any arrears) paid by the taxpayer. During the time period we consider the control group has paid roughly 10 percent of their total bill on average, and we find that treated taxpayers pay an additional 1.6-1.9 percent of their bill on average. Only 8.4 percent of control group taxpayers paid off their entire bill. Those receiving a reminder or a reciprocity message were 1.6-2 percentage points more likely to fully pay. Again, reciprocity performed better than the other message types, although not significantly so.

To check whether the timing of the messages across groups affected the impacts, we include analysis of our main results – whether citizens paid any part of their bill and the amount that they paid – for the subgroup that received messages on June 26 or later (Appendix Figure A1). Our pattern of results is consistent in this smaller sample. The impact on payment rates is higher for those who received any treatment, and the point estimate is highest for the 10