Is this a subscription service? Or do I have to purchase this data each year?

It's a 1 time fee, not a subscription. And for that 1 time fee, you get the most current Census demographics available at this time.
Do I get updates as new data are released?
Next year's data isn't included in the price of this year's dataset, and you could choose to buy next year's data when it's available (typically in December).
For small geographies like zips/ZCTAs, the US Census Bureau collects surveys for 5 years and then sums up the responses to produce current year estimates. For the 2021 dataset, surveys were collected in 2021, 2020, 2019, 2018, and 2017. Then, the later year survey responses were projected forward (e.g. 2017 income was projected into 2021 dollars). 
The 2020 dataset is made up of surveys that were collected in 2020, 2019, 2018, 2017 and 2016. There are 4 years of overlapping survey results between the 2021 dataset and the 2020 datasets.   What this means to you is that there won't be a lot of change between 2021 data and 2020 data. Most of our clients wait 2 to 3 years before buying a more current dataset.

The only clients who get year over year updates are those clients, who for marketing purposes, have to be able to say "we are using the most current US Census data." So marketing drives the data update decision rather than changes in statistics for these clients.

Consider reading the related FAQ of Should I compare data year-over-year?
Did this answer your question? Thanks for the feedback There was a problem submitting your feedback. Please try again later.