As background, the Postal Service developed a process (model) to estimate the deferred revenue for prepaid postage (PIHOP) at the end of a reporting period. This audit found that changes in consumer purchase and usage behaviors associated with the introduction of the Forever Stamp explained, for the most part, recent significant fluctuations in the PIHOP liability. Further, the Postal Service's mandated quarterly financial reporting highlighted the changes to the PIHOP estimate. However, we identified opportunities that could improve the predictability and financial transparency of the PIHOP estimate. Read the report!