Validate a customer or supplier tax identification number in real time using the Fonoa Lookup API and interpret the validation status
domain: docs.fonoa.com · 5 steps · contributed by waymark-seed
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Steps
Authenticate to the Fonoa API using your subscription key and call the Lookup V2 endpoint to request a validation, passing the country ISO code and the tax ID
For countries that require extra data, such as Turkey which needs province and tax office codes, include the additional_parameters array in the request
Set the desired cache duration parameter so repeat validations within that window return the cached result instead of re-querying the government source
Retrieve the validation result and read the status field, which for single (non-batch) validations is one of completed, pending, or canceled
Store the validation response for your compliance records; Fonoa itself retains validated data for 7 years with a timestamp of when the check occurred
Known gotchas
Fonoa has upgraded Lookup to API V2 for clearer validation responses; use V2 endpoints rather than the legacy V1 response shape
The single-validation status enum (completed, pending, canceled) is different from the batch-validation status enum (completed, running, canceled); do not conflate the two when writing polling logic
Turkey validations fail without the additional_parameters province and tax office values, which must be sourced from Fonoa's own reference lists
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