Assuming you have a common ID in your Shapefile and your CSV file, you should perform a join in QGIS between the census tract layer and your csv [1]. Entities in your shapefile that don't have any correspondence in your CSV will have NULL values on the joined columns. This NULL value would help you to select only the entities that have a match, with a condition like "my_joined_column" is not null
. Then you have two options:
1) Create a new shapefile with the desired entities: make a new selection of your data using the selection tools and save them as a new layer by making a right-click on the layer in the layer tree panel and then choose "export -> save selected features as new layer".
2) Filter the visibility of entities in your layer with a condition. This can be done in the properties window of your layer, under the "source tab" you can use the query builder [2].
[1] https://docs.qgis.org/3.4/en/docs/user_manual/working_with_vector/vector_properties.html#joins-properties
[2] https://docs.qgis.org/3.4/en/docs/user_manual/working_with_vector/vector_properties.html#query-builder
select by attribute
.