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Trial Title
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Voice and Tax Compliance: Experimental Evidence from Kenya
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Tax Morale and Institutions: Experimental Evidence from East Africa
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Abstract
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Before
This study uses a randomized controlled experiment to test whether government-issued text messages that invite taxpayer input on public spending can improve property tax compliance among registered property owners in Nairobi County, Kenya. Before the tax deadline, the relevant tax and government authority sends two rounds of SMS messages to property owners randomly assigned to one of two treatment groups: a payment reminder that also invites them to indicate which local spending category should receive funding priority, or the same payment reminder without the invitation. A control group receives no message. Tax compliance is measured using administrative payment records (any payment, amount paid, share of bill paid). After the deadline, both treatment groups receive a single SMS eliciting beliefs about whether the county government responds to resident input; comparing beliefs and payments across groups tests whether any compliance response reflects belief updating rather than alternative explanations. A follow-up SMS survey measures beliefs about the use of tax revenue, attitudes toward government, institutional trust, and perceptions of public service quality.
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After
This study uses a randomized placebo-controlled experiment to test whether text messages from the county government that give residents voice over local spending priorities, provide reciprocity information about planned county spending, or both, increase tax morale and improve beliefs about county government in Nairobi County, Kenya. Nairobi County sends a single SMS to residents with mobile numbers in county records, randomly assigned to one of five equal groups: an invitation to reply indicating which of two county project areas, roads/drainage or healthcare, is most important to them (voice); information that the county is planning projects in these areas (information); both the information and the invitation (voice and information); a county message about office hours with no spending content (placebo); or no message (control). The two project areas are the categories most often selected in a pilot SMS that asked about 1,000 residents which county service problem most needs fixing in their neighborhood. All five groups are then invited from a research number to complete a short endline survey measuring tax morale, perceived spending quality, perceived responsiveness of elected councilors, self-reported payment of property rates, trust in county and national institutions, preference between local and higher levels of government, access to public services, service priorities, and recall and credibility of the message. Comparing the voice and information arms with the placebo separates message content from the act of receiving a message from the county; the endline survey measures whether the messages move beliefs about responsiveness and reciprocity, tax morale, and self-reported payment.
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Trial Start Date
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June 14, 2026
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October 19, 2026
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Trial End Date
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October 01, 2026
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November 19, 2026
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Last Published
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June 17, 2026 09:05 AM
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October 16, 2026 01:42 PM
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Intervention Start Date
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June 14, 2026
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October 19, 2026
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Intervention End Date
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October 01, 2026
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November 19, 2026
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Primary Outcomes (End Points)
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Before
The key outcome variable is tax compliance, measured by total taxes paid and the percentage of taxes paid. Tax morale, measured by the responses to our survey, is also a key outcome variable.
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(1) Tax morale, measured by the endline item asking whether a taxpayer who underreports to pay less tax is doing something not wrong at all, wrong but understandable, or wrong and punishable. (2) Perceived responsiveness, measured by the endline item asking how likely it is (0 to 100) that residents could get together and make their elected councilor listen to a matter of community importance. (3) Perceived spending quality, measured by the endline item asking how well Nairobi County uses tax money (0 to 100).
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Experimental Design (Public)
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Before
Registered property owners with property tax obligations in Nairobi County, Kenya, are randomized between one control and two treatment groups, based on message content: no message (control), an SMS reminding owners of the upcoming property tax deadline, or the same reminder together with an invitation to indicate which local spending category should receive funding priority. The two treatment groups receive two rounds of SMS messages before the tax payment deadline. After the deadline, both treatment groups receive a single SMS eliciting beliefs about whether the county government responds to resident input; comparing beliefs and payments across groups distinguishes belief updating from alternative explanations for any compliance response. Following the government's delivery of the SMS messages, all participants are invited to complete an SMS survey. The survey includes items on moral attitudes toward non-payment, message recall and credibility, perceived use of tax revenue by the county and national government, trust in public institutions, ease of access to public services, and demographic information. Survey responses are incentivized through a lottery.
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After
Nairobi County residents with mobile numbers in county contact records are randomized into five equal groups defined by the content of a single SMS sent by Nairobi County. T1 (Voice): the message states that the county is planning projects that improve Nairobi and invites the recipient to reply 1 for roads/drainage or 2 for healthcare to indicate which is most important. T2 (Information): the message states that the county is planning projects that improve Nairobi, including paving new roads and constructing new hospitals. T3 (Voice and Information): the information in T2 followed by the invitation in T1. P (Placebo): a county reminder of sub-county office and Huduma Centre opening hours, with no reference to spending or taxes. C (Control): no message. The design is a 2 x 2 factorial in voice and information; the placebo arm separates message content from the effect of receiving any message from the county, and the no-message control provides a baseline for all endline outcomes. Project areas and content are drawn from the Nairobi County 2025/2026 Annual Development Plan and were selected from a pilot SMS in which about 1,000 residents chose among ten county service areas. After the treatment round, all five groups receive an identical SMS from a research number inviting them to a five-minute endline survey on county services, incentivized by lottery [ten prizes of KES 10,000, or one prize of USD 1,000, per the approved consent]. The survey covers tax morale, self-reported payment of property rates, property ownership, payment of county fees, whether local government serves constituents better than higher levels, message recall, attributed sender and credibility, perceived spending quality, trust in the President, County Governor, Kenya Revenue Authority and County Assembly, perceived responsiveness of the elected councilor, presence of public facilities within walking distance, and ranking of county service priorities. Pre-specified comparisons are T1 and T3 vs. P (voice), T2 and T3 vs. P (information), the voice x information interaction, and P vs. C (any county message).
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Randomization Unit
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Individual property owner
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Individual taxpayers
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Planned Number of Observations
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We plan to sample 150,000 property owners; the analysis on tax compliance will be done on the subsample that has not made payments by the treatment date.
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Planned number of observations: 471,935 Nairobi County residents with mobile numbers in county records. All outcomes are measured on endline respondents; at the 5 percent response rate assumed in the pre-analysis plan, about 23,600 respondents, roughly 4,700 per arm.
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Sample size (or number of clusters) by treatment arms
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For each treatment arm, we will sample 50,000 owners. These owners will be sampled proportionally across the different wards.
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94,387 individuals in each of five arms: 94,387 control (no message); 94,387 placebo (county office-hours message); 94,387 voice; 94,387 information; 94,387 voice and information. Total 471,935 individuals, allocated proportionally across the 85 electoral wards of Nairobi. All outcomes are measured on endline survey respondents; assuming 90 percent SMS delivery and a 5 percent survey response rate, approximately 4,250 respondents per arm, about 21,000 in total.
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Secondary Outcomes (End Points)
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Reply to the voice invitation in T1 and T3: any reply, and roads/drainage vs. healthcare. Endline items: self-reported payment of property rates in the current period; trust in the President, County Governor, Kenya Revenue Authority and County Assembly (1 to 7); whether local governments serve constituents better than higher levels of government; message recall, attributed sender and perceived truthfulness; ownership of property subject to local property rates; payment of non-tax fees to the county in the last six months; presence of a post office, school, police station and health clinic within walking distance; ranking of county service priorities; and survey response rate by arm.
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