404 for an unknown UPRN, costs nothing.
There is no session token to create or send. Search sessions are opened and settled by the server.
Charges by endpoint
Reverse, bulk and cleanse responses are charged at the
address_uprn or address_base rate according to the source of the addresses returned. The pricing page in the dashboard lists every rate, including any your agreement changes.
Search sessions
GET /v1/search/suggest is not charged per request. When a query narrows to 100 or fewer addresses, the response carries a search_id and a search session opens. Each session costs 1 credit, charged about 11 minutes after it opens, whether or not you then look an address up.
A later query whose addresses all fall inside one of the last eight sets returned to the same API key in the past 10 minutes joins that session rather than opening a new one, whether or not you send the search_id back. Sending it back narrows within the set without fetching again.
The full record for the address the user picks comes from GET /v1/address/uprn/{uprn}, charged as above. A search that ends in a selection is charged for its session and for that lookup.
If you send X-API-Version with a release earlier than 3.0.0, such as 2.150.0 (see Versions), suggest uses its earlier format: there are no sessions, and each request that returns at least one address is charged once at the address_base rate. Accounts kept on that format are charged the same way.
Repeat lookups and retries
By default, every successful request is charged, including a lookup of an address you have retrieved before. A retry of a request that completed on the server, for example after a timeout on your side, is charged again. Distinct-record billing can be set for an account by agreement. With it, each address, street or property record is charged at most once per line item in each licence year. Each licence year runs from the anniversary of the date your organisation first registered. Postcode lookups and search sessions are still charged every time.Checking a charge
A charged response usually carries billing headers, includingX-Credits-Charged. Usage and limits explains them and where else to see what you spent.