Guide
Third Party Designee on SS-4 (2026) Guide
The third party designee on Form SS-4 Line 18 authorizes someone to receive your EIN on your behalf. ein.so serves as third party designee for non-US residents. $49 Standard. $97 Express.
The third party designee on Form SS-4 (Line 18) is the person or organization the IRS authorizes to receive your EIN and discuss the application on your behalf. The authorization covers the EIN application only. It ends once the IRS assigns your EIN. When you use ein.so, we serve as your third party designee. We receive your EIN directly from the IRS and deliver it to you by email. Standard filing costs $49 (4-7 business days). Express costs $97 (2-3 business days).
The third party designee field sits at the bottom of Form SS-4, just above the signature block. It tells the IRS where to send the EIN and who may answer questions about the application. Most non-US residents use a designee because the IRS online EIN tool requires a Social Security Number, which they do not have. The fax method, filed through a designee, is the working path. This guide explains exactly what the third party designee does, how it differs from the responsible party, when to use one, and how ein.so acts as your designee.
| Detail | Information |
|---|---|
| Location on SS-4 | Line 18 (third party designee) |
| Purpose | Authorizes a party to receive the EIN on your behalf |
| Required? | No (optional) |
| Authorization scope | EIN application only |
| Who typically uses it | EIN services, CPAs, attorneys |
| ein.so role | We are listed as your designee |
| Fields completed | Name, phone, fax |
What It Is
What Does the Third Party Designee on SS-4 Authorize?
The third party designee on Line 18 authorizes one party to receive your EIN and answer IRS questions about the application. The authorization is narrow. It covers the single EIN application and nothing else. It ends when the IRS assigns your EIN.
The designee gains three specific abilities during the application:
Receive the EIN
Answer IRS Questions
Limited Time Window
The designee never owns or controls your EIN. You stay the responsible party on Line 7a. See the full SS-4 form guide for every field on the form.
Designee vs Responsible Party
How Is the Third Party Designee Different From the Responsible Party?
The third party designee on Line 18 only receives the EIN, while the responsible party on Line 7a controls the entity. These two roles are separate and never interchangeable. The responsible party stays on file permanently. The designee authorization ends in days.
People confuse these two fields constantly. The table below makes the difference exact.
| Factor | Responsible Party (Line 7a) | Third Party Designee (Line 18) |
|---|---|---|
| Role | Controls the entity and its funds | Receives the EIN on your behalf |
| Required? | Yes, always | No, optional |
| Who it is | A natural person (owner/manager) | Often a service, CPA, or attorney |
| Duration on file | Permanent | Ends when EIN is assigned |
| Signs the form? | Yes | No |
| Identification used | Passport number on Line 7b | Name, phone, fax only |
| Can handle later IRS matters? | Yes | No |
The responsible party must be an individual, not a company. For a non-US resident, you enter your full passport name on Line 7a and your passport number on Line 7b. Read the dedicated responsible party guide for the rules the IRS applies to Line 7a. For applicants without a Social Security Number, the EIN without SSN guide explains why the passport number replaces the SSN.
When to Use
When Should You Use a Third Party Designee on Form SS-4?
You use a third party designee when someone other than you files Form SS-4 and needs to receive the EIN. You leave Line 18 blank when you file the form yourself. The choice depends entirely on who submits the application.
The four common scenarios are listed below.
You Use ein.so
You Use a CPA
You Use an Attorney
You File Yourself
The IRS online EIN application is restricted to applicants with a valid SSN, ITIN, or existing EIN. Non-US residents who lack all three must file by fax or mail. The fax method, filed through a designee, returns the EIN in 4-7 business days. See EIN for non-residents for the complete non-resident path.
How to Complete Line 18
How Do You Complete the Third Party Designee Section on SS-4?
You complete the third party designee section by entering the designee's name, phone number, and fax number on Line 18. The designee does not sign the form. The responsible party signs the signature block below Line 18. The fields are short and require no identification numbers.
Enter the Designee Name
Add the Designee Phone Number
Add the Designee Fax Number
Sign as the Responsible Party
Line 18 Field Reference
| SS-4 Field | Entry |
|---|---|
| Designee name | The party receiving the EIN (e.g., ein.so) |
| Designee phone | A number the IRS can call during US hours |
| Designee fax | The fax number for the EIN assignment letter |
| Signature block | Signed by the responsible party only |
The designee fields require no SSN, ITIN, or EIN. Only the responsible party section (Line 7b) carries an identification number, which for non-US residents is the passport number. See the EIN by fax process for how the IRS returns your EIN to the designee fax line.
ein.so as Designee
Why Does ein.so Serve as Your Third Party Designee?
ein.so serves as your third party designee because the IRS sends the EIN to the designee fax line, which lets us receive your EIN and deliver it the same day. We file Form SS-4 to the IRS fax number 855-215-1627 with ein.so listed on Line 18. The IRS faxes your EIN to us, and we email it to you.
This arrangement solves the problems non-US residents face when filing alone.
No US Phone or Fax Needed
No International IRS Calls
Same-Day EIN Delivery
You Keep Full Control
The IRS charges $0 for an EIN. The ein.so fee covers the form preparation, the fax filing, the designee role, and the delivery. Compare the full breakdown on the EIN cost page.
What the Designee Cannot Do
What Can the Third Party Designee Not Do?
The third party designee cannot file your taxes, change your address, or act on any IRS matter beyond the single EIN application. The authorization is one of the narrowest the IRS grants. It ends the instant the IRS assigns your EIN.
These limits protect you. The designee role is built to receive an EIN and nothing more.
Limits of the Designee Authorization
- The designee cannot represent you in an audit or tax dispute.
- The designee cannot file your annual returns or information returns.
- The designee cannot change your responsible party or business address with the IRS.
- The designee cannot access your tax account or transcripts.
- The authorization expires the moment the IRS issues the EIN.
For ongoing IRS authority, you file a separate form. Form 2848 grants power of attorney for representation. Form 8821 grants tax information access. Neither is part of the SS-4 designee role. ein.so files the SS-4 and acts as designee only. We do not provide tax advice. Confirm any tax representation needs with a CPA.
After you receive your EIN, your real compliance work begins. A foreign-owned single-member US LLC files Form 5472 with a pro-forma Form 1120 each year. The penalty for not filing is $25,000. Most LLCs also file a BOI report with FinCEN.
After Your EIN
What Happens After the Designee Receives Your EIN?
After the designee receives your EIN, you use it to open a US bank account, set up payments, and meet annual filing duties. The designee role is finished at this point. You hold the EIN as the responsible party and move into operating your US business.
Immediate Next Actions With Your EIN
- Open a US business bank account using the EIN for a bank account guide. Mercury and Relay accept non-resident LLC owners remotely.
- Connect payment processors like Stripe and PayPal to your US entity.
- File your BOI report with FinCEN, free at fincen.gov/boi.
- Track your annual Form 5472 deadline to avoid the $25,000 penalty.
- Need a personal taxpayer ID too? Compare the ITIN service: $197 standard or $297 express.
The EIN is your federal tax ID. It links your foreign-owned LLC to the US financial system. The designee delivered it; you now own it. Confirm your specific US and home-country tax obligations with a CPA, as ein.so does not give tax advice.
Next Steps
Get Your EIN Through ein.so as Your Designee
ein.so prepares Form SS-4, lists itself on Line 18, faxes the application to the IRS, and emails your EIN. The full path is below.
- Apply now — start your SS-4 with ein.so as your third party designee
- Read the SS-4 form guide — every line explained, including Line 7a and Line 18
- Learn how to get an EIN — the complete application process for non-residents
- Get an EIN without an SSN — the passport-number path on Line 7b
- See EIN processing time — 4-7 business days Standard, 2-3 Express
- Review EIN cost — the IRS charges $0; our fee is $49 Standard or $97 Express
Related guides: EIN for non-residents | Responsible party | EIN by fax | EIN for a bank account | Form 5472 | BOI filing.
Frequently Asked Questions
What is a third party designee on Form SS-4?
A third party designee is the person or organization named on Line 18 of Form SS-4. The IRS authorizes this party to receive your EIN and answer questions about the application. The authorization covers the EIN application only. It ends once the IRS assigns and delivers your EIN. ein.so acts as your designee.
Is the third party designee section required on SS-4?
No. The third party designee section on Line 18 is optional. If you leave it blank, the IRS sends the EIN directly to the responsible party on Line 7a. If you list a designee, the IRS sends the EIN to that party. Use a designee when a service like ein.so files your SS-4 for you.
Who should I list as my third party designee?
List the party who files Form SS-4 for you. If you use ein.so, list ein.so. If a CPA or attorney files for you, list that professional. If you file Form SS-4 yourself, leave Line 18 blank. The IRS then returns the EIN directly to the responsible party named on Line 7a.
Is the third party designee the same as the responsible party?
No. The responsible party on Line 7a is the individual who controls the entity and its funds. The third party designee on Line 18 only receives the EIN on your behalf. The responsible party stays on file permanently. The designee authorization ends the moment the IRS issues your EIN.
Does using a third party designee change who controls my EIN?
No. The third party designee never owns or controls your EIN. The designee receives the assignment letter and forwards it to you. You remain the responsible party named on Line 7a. ein.so delivers your EIN by email and never holds authority over your LLC, bank account, or tax filings.
How long does the third party designee authorization last?
The third party designee authorization lasts only through the EIN application. It expires when the IRS assigns and mails the EIN. The designee cannot file your taxes, change your address, or act on other IRS matters. For ongoing IRS representation, you file a separate Form 2848 or Form 8821.
Can a non-US resident use a third party designee on SS-4?
Yes. Non-US residents use a third party designee because they cannot use the IRS online EIN tool, which requires an SSN. ein.so files Form SS-4 by fax to 855-215-1627 using your passport number on Line 7b, lists itself on Line 18, and emails your EIN in 4-7 business days for $49.
Can I change the third party designee after filing SS-4?
No. You cannot change the third party designee on a submitted Form SS-4. The Line 18 authorization is fixed for that single application. If the designee changes before filing, you correct Line 18 first. After the IRS issues the EIN, the designee authorization ends automatically and cannot be transferred.
Does the third party designee need to sign Form SS-4?
No. The third party designee does not sign Form SS-4. The responsible party signs the form in the signature block. The designee completes only the Line 18 name, phone, and fax fields. The signature certifies the information is correct, so the responsible party, not the designee, signs the application.
Need an EIN? We Handle Everything.
Non-US resident? We file Form SS-4 with the IRS and deliver your EIN by email. Just $49.
Get My EIN for $49