How we verify fax numbers
The fax numbers people find online are often wrong, stale, or internal-only, and a document sent to the wrong number can miss a deadline. These are the exact rules we follow when we build the XenFax fax directories — with real examples of numbers we excluded and conflicts we chose to disclose rather than hide.
1. Official sources only
We publish a fax number only when we can confirm it on the institution's own official domain or an official PDF it publishes — for example irs.gov, static.usaa.com, edd.ca.gov, or dol.ny.gov. We do not copy numbers from directory sites, form-filler sites, or forums, because those repeat each other without a primary source. If the only place a number appears is an aggregator, it does not go on the page.
2. Every number is dated and linked
Fax numbers change when institutions reorganize, so a number is only as trustworthy as its date. Every directory page carries a Last verified line and a link back to the official source we checked, so you can confirm it yourself in one click and always know how fresh it is. We tell you to re-confirm against that source before sending anything sensitive.
3. Unverifiable numbers are omitted — and we say so
When an institution does not publish a fax number for a task, we do not invent one to fill the gap. The page states plainly that no official fax number exists and documents the channels the institution actually supports — secure message, online upload, phone, or mail. Across the bank and mortgage-servicer directories you will see several entries marked exactly this way rather than padded with unconfirmed numbers.
4. Internal-only numbers are excluded
Some fax numbers that circulate online are internal case-routing lines that were never published for public use. Listing them looks helpful but sends people's documents to the wrong place.
Real example — IRS Form 433-D. Aggregator sites circulate an internal IRS e-fax (EEFax) number as “the 433-D fax number.” Form 433-D (an installment agreement) is case-specific: the IRS routes it to the office handling your account, and there is no general public fax line for it. So our Form 433-D page deliberately publishes no general fax number and instead tells you to use the address or fax number printed on your own IRS notice, or the number your assigned revenue officer gives you.
5. Conflicting official sources are disclosed side by side
Sometimes two official pages from the same institution disagree. Rather than silently pick one, we show both and flag the discrepancy so you can confirm the right one before you send.
Real example — New York DOL. Two official dol.ny.gov pages currently list different unemployment-insurance fax numbers: 518-457-9492 on the Unemployment Insurance Contact page and 518-457-9378 on NY DOL's “Contact Information for Customers” (form P813). Because we cannot resolve which is current from the outside, our New York DOL page shows both, explains the conflict, and recommends confirming against your own determination notice — or with the Telephone Claims Center — before faxing.
6. Re-verification and corrections
We re-check the directories against their official sources on a rolling basis and update the Last-verified date whenever we do. Because institutions can change a number the day after we check, we always ask you to confirm against the linked source before sending. If you find a number that is out of date or wrong, email us at hello@xenfax.com and we will re-verify it against the official source and correct the page.