In most cases the application travels with the return that needs it rather than going in on its own. The number exists to let a filing or a claim happen, so the first question is which return or claim is driving it. There are situations where a number is needed for something other than a return, and a withholding certificate on a property sale is the common one. Those are handled differently. Working out which of the two you are in decides what goes in the envelope.
Who files Form W-7?
- 15+Years of the founder's cross-border experience
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Non-resident filers, spouses and dependants who must file or be claimed on a US return, and non-resident sellers of US property. The obligation is decided by facts rather than by tax owing, which is why a nil position does not remove it.
The rule on who files
Non-resident filers, spouses and dependants who must file or be claimed on a US return, and non-resident sellers of US property.

When it does not bind you
The number is the gate. Withholding refunds, treaty claims and property-sale certificates all stall without it, identity documents must be certified in a specific way, and the application usually travels with the return that needs it.
Your next step
The full treatment — who it binds, the deadline, the penalty and the fixed fee — is on W-7 — ITIN application. We would rather scope it properly than quote it quickly.
Checked and signed off for the 2025 and 2026 filing seasons by Udit Gupta, International Tax, Cross-Border Tax & Transfer Pricing Expert, Legal Quotient Consultants. This is general information rather than advice about your file — a short call is the way to get the second.
Cross-border situations we are engaged for
Non resident seller needed a number before the closing could settle
A vendor selling a US property discovered, close to completion, that the certificate reducing the withholding at closing could not be applied for without a tax number. We prepared the application, arranged for the identity documents to be certified acceptably, and filed it with the certificate request. The engagement produced an issued number and a filed certificate request, and with them a documented basis for the amount withheld at closing rather than the full default sum held back against a later claim.
Read how this one runsSpouse added to a joint return that had been waiting on a number
A client's return could not be filed on the basis he wanted, because his wife had no US tax number and was not eligible for one. We prepared her application, dealt with the certification of her identity documents, and filed the application together with the return it supported. What the engagement produced was a return filed on the intended basis, with the number and the claim arriving as one submission rather than a filing made now and corrected later.
Read how this one runsTreaty claim on royalty payments held up for want of a number
A non-resident author was having tax withheld on royalty payments at the default rate, because the claim reducing it had nowhere to attach. We identified the filing the claim had to sit behind, prepared the number application with certified identity documents, and submitted them together. The engagement produced an issued number, a filed claim on the record for the payer to work from, and a documented position on the rate to apply to payments going forward.
Read how this one runsIdentity documents certified so the client kept his passport
An applicant had abandoned an earlier attempt rather than post his passport abroad, and had gone two filing seasons without the number he needed. We arranged certification of the identity documents in a form that would be accepted while the originals stayed with him, and filed the application again. The engagement produced an issued number and a record of how the documents had been certified, which he could point to when the same question came up for his children the following year.
Read how this one runsDependants' applications filed as a set with the return claiming them
A family needed numbers for two children who were being claimed on a US return, and had been filing without them. We prepared an application for each child, with its own certified identity documents, and filed the set with the return that claimed them. What the engagement produced was a filed return whose dependant claims were supported by applications submitted at the same time, and a single file of the family's certified documents for use in later years.
Read how this one runsWithholding on rental payments reclaimed once the number existed
An owner of US rental property had tax withheld at source for years and had never filed, because she had no tax number and no clear idea where to start. We prepared the application, dealt with the identity documents, and filed it with the first of the returns reporting the rental income on the basis she was entitled to use. The engagement produced an issued number and filed returns for the open years, putting the over-withheld amounts into a claim instead of leaving them unclaimed.
Read how this one runsWhether the Year Made Someone an NRI
Indian residence is decided by presence tests applied to the financial year, and a single trip can change the answer for the whole of it. The status is established before any return or exemption is considered.
Read how this one runsDocumentation Requested, and the Deadline Is Not Extendable
Contemporaneous documentation has to exist by the filing deadline, not be assembled when it is asked for, and the penalty protection turns on that timing. The engagement produces the analysis for the year in question and puts a repeatable process behind the next one.
Read how this one runsAll case studies — every published engagement in one place.
Core International & Cross-Border Tax Services
Strategy and compliance for income, assets and families spread across borders.
Industries & Client Types We Serve Worldwide
- Foreign VAT / GST / sales tax registrations
- Marketplace withholding reviews
- Inventory nexus & PE analysis
- Multi-currency books reconciled
- Cross-border revenue sourcing & withholding
- IP structuring with real substance
- Equity for cross-border teams
- U.S. expansion: entity & PE setup
- Reg 105 / 102 waivers
- Permanent establishment risk
- Partner mobility planning
- Cross-border withholding recovery
- Section 216 rental returns
- FIRPTA withholding recovery
- Section 116 clearance
- Treaty credit optimization
- Transfer pricing documentation (s.247)
- Customs value vs transfer price
- Foreign affiliate reporting (T1134)
- Country-by-country reporting
Performance income is taxed where earned — Regulation 105 in Canada, withholding agreements in the U.S. — with special treaty articles overriding the usual rules.
Performance income is taxed where the performance happens, and the deduction is usually taken at source on the gross fee before expenses. Recovering the difference is a filing exercise in the other country, and it only works if the tour, the residency and the withholding certificates were documented while the work was being done.
- Reg 105 & U.S. CWA agreements
- Multi-state & country calendars
- Touring income allocation
- Royalty & image-rights withholding
- Residency analysis before moving
- Employer payroll exposure
- Totalization & social security
- Foreign tax credits
- Treaty access & PPT reviews
- FAPI & surplus computations
- Withholding-efficient routing
- Governance & substance
What people ask us about Form W-7
If your spouse has to be on the return and is not eligible for a social security number, then yes, the number is what puts them there. The application is prepared with the return and the two are filed together. What delays these is almost never the form. It is the identity documents, which have to be certified in a particular way before they will be accepted. We sort the documents out before anything is submitted, because a return held up waiting on a number is also a return that is not yet filed.
Non-resident sellers of US property are squarely in the group who need the number, and the timing is what causes the pain. The number is a gate. The withholding certificate that reduces what is held back at closing, and the return that reclaims an over-withheld amount afterwards, both stall without it. Sellers usually discover this in the week the sale is closing, which is the worst moment to be gathering certified identity documents. Started early it is administration; started late it is money sitting with the tax authority for a year.
Identity documents have to be certified in a specific way, and an ordinary photocopy is the most common reason an application comes back. That is also why people put off applying, since nobody wants to post an original passport abroad and wait. The practical route is to have the documents certified acceptably so the originals stay with you, and to arrange that before the return or the claim is ready to go, rather than discovering the requirement when everything else is finished.
Dependants who are claimed on a US return and cannot obtain a social security number need their own numbers, one each. The applications are prepared alongside the return that claims them, and each needs its own certified identity documents, which for children is the part families underestimate. We prepare the household's applications as a set and file them with the return, so the claim and the numbers supporting it arrive together instead of the return going in and being adjusted while the numbers catch up.
Because the number is the gate, and nothing downstream of it moves. A repayment of over-withheld tax, a treaty claim that reduces the rate on a payment, a certificate on a property sale: each needs a filer the system can identify, and until the number exists there is no filer. It is rarely a question of the claim being wrong. It is that the claim has nowhere to attach. Applying for the number and filing the claim it supports as one exercise is what shortens the wait.
By default the payer or agent withholds a flat rate on the gross rent and remits it, with no deduction for mortgage interest, taxes or repairs. Electing under section 216 lets you file on the net rental result instead, which for most properties recovers a substantial part of what was withheld; an NR6 undertaking filed before the year starts lets the withholding itself be computed on net rather than gross. See the section 216 return.
Canada's flat withholding on certain payments to non-residents — dividends, interest to related parties, rents, royalties, pension and annuity payments, management fees. The payer withholds and remits, and is liable if they do not, which is why they insist on documentation. A treaty can reduce the rate, but only where the recipient has given the payer the declaration establishing entitlement before payment. Where too much was withheld, a refund claim is the route, with its own time limit. See Part XIII withholding review.



