The HCT costing tool is a simple tool that can be used for costing HIV testing. The model is flexible, allowing for multiple different testing modalities and scenarios to be run and compared concurrently. All testing is assumed to follow a cascade or algorithm consisting of different steps (at the least, pre-test counselling, testing using rapid tests +/- confirmatory tests as appropriate, post-test counselling). The cost for each step is calculated separately and then combined for a total cost per modality, allowing for patients to decline proceeding at any stage while still including the costs incurred up to that point. The results are cost per positive test and the cost per negative test of each modality which can then be compared. Instructions on using the model have been added to each input sheet.