TIN validation improves onboarding data quality by catching errors in tax identification numbers as they are collected. When those errors are corrected during onboarding, fewer mistakes reach account records and tax reports. Consistent formatting alongside these checks makes the numbers easier to compare across records.
Errors are caught while they are still easy to correct
Suppose an investor leaves a digit out of their tax number. Without a check, that incomplete number can pass from onboarding into account records and tax reporting. Each team using it inherits the same mistake.
A length check can catch the missing digit. Some tax numbers also include a check digit calculated from the other digits. Entering 54 instead of 45 keeps the length the same, but may make the check digit stop matching. This can reveal a typo in a number that otherwise looks right.
During onboarding, the person is still there to check the number against their document. If the error is discovered months later, the team may have to get back in touch, wait for a reply and find out where the old value has been used.
The OECD's tax reporting handbook makes this connection too: checking TIN formats can improve the information collected and reduce follow-up over incorrect numbers.
In FATCA reporting, an incorrectly formatted US TIN can trigger an IRS error notification and require a corrected record to be submitted. An entry mistake can become another round of reporting work.
The right checks for the tax number requested
The checks need to match the country and the type of tax number being collected. In France, for example, a personal tax number has 13 digits, while a SIREN business number has nine. A valid SIREN would still be the wrong answer to a request for someone's personal tax number.
Validation can flag this kind of mix-up. If someone is unsure what their local tax number looks like or where to find it, examples and guidance can help them correct the entry.
The TIN Validate API can run these checks during onboarding and return the outcome of each one. Knowing why an entry failed makes it easier to explain the problem and collect a corrected number.
The same number is recorded consistently
Validation checks whether a number follows the applicable rules. Normalisation is a separate step that puts equivalent ways of writing it into a consistent format.
Two systems may hold the same tax number, one with spaces and one without. An exact comparison can miss the match. Where those spaces are only formatting, storing a consistent version removes that avoidable mismatch and makes it easier to identify possible duplicate records.
For example, a Dutch BSN can be written as eight digits when its leading zero is left off. TIN Validate restores that zero before running its checks. For a valid entry, the returned nine-digit form provides a consistent value to store.
The API also returns the original entry alongside the formatted result. A system using it can retain both to show what was submitted and how it was recorded.
What a valid result tells you
A passing result means the number meets the rules that were checked. It does not establish that the number has been issued or belongs to the person providing it. Confirming that requires separate verification.
Correcting the number during onboarding means less follow-up when the records are needed for reporting.