In this study, we first present a large natural field experiment that tested messages
aimed at increasing tax compliance. We find that the main drivers of changes in
compliance are messages describing the monitoring and enforcement behavior of
the tax collector. A second natural field experiment built on the results of the first
experiment to further investigate what kinds of costs resulting from tax collector
oversight are salient to taxpayers. Specific time and cognitive incentives did not
significantly increase payment rates, whereas stating non-specific costs of inaction
did. Additional analyses suggest the increase in compliance is likely due to a 'fill
in the blank' effect in which taxpayers assume the consequence is a fine.
Interestingly, specifically stating maximum fine or jailtime consequences have the
largest effect in a laboratory setting but only if the consequences are interpreted as
realistic. Overall, our study reinforces that tax authorities can use short messages
to increase tax compliance; the estimated accelerated revenue from the two field
studies amounts to 9.9m GBP.