"Pickups" is a term commonly used in the world of assessing that refers to the annual inspection of those properties that have undergone some form of "new construction". This is the process by which an assessor visits any and all properties that have undergone renovations, additions, deletions or the completion of renovation or additions started in the previous year. This information is generally received through inventories or building permits.
The assessor is required to assess these changes as they existed on April 1st of each year and not after. In other words, if a property owner adds an addition or renovates their home after April 1st, it is not assessed until the following April 1st. Likewise, if a structure existed on the property on April 1st but was subsequently removed on July 15th, that structure is still assessed (and taxed) until the following April 1st.