Starting a U.S. company as a non-U.S. founder is already complicated, but one of the most confusing parts comes when it’s time to actually send your tax forms to the IRS. Filing taxes isn’t just about preparing the forms—it’s also about how and where they get submitted.
Many foreign founders are surprised to learn that some IRS forms can only be mailed, others can be faxed, and only certain returns can be e-filed. And mailing from outside the U.S. can cause delays, lost paperwork, and serious stress.
This guide explains the different ways U.S. federal tax forms are submitted, why foreign founders often run into problems, and how working with Bookmate makes the process far smoother.
Why tax submission is a stress point
For U.S. residents, tax filing is relatively straightforward—most accountants e-file returns, and the IRS confirms receipt. But for foreign founders, the situation is very different. Many key forms for foreign-owned companies, such as Form 5472 attached to a pro forma 1120, cannot be e-filed.
They must be submitted by fax or physical mail. If you live outside the U.S., that means international postage, longer delivery times, and the risk of documents getting lost before they reach the IRS.
Even when forms can be mailed, the addresses vary depending on the type of return and whether a payment is included. Choosing the wrong address can result in months of delay, with the IRS eventually sending penalty notices because they didn’t process the form on time.
These headaches are especially common for founders trying to handle filings themselves from abroad.
Methods of submitting federal tax forms
1. E-filing
Some returns, like Form 1120 (corporate tax return) and Form 1065 (partnership return), can be e-filed. E-filing is fast, secure, and gives you immediate confirmation that the IRS received your return. However, not every form can be e-filed, especially those related to international reporting.
2. Fax
Certain forms, including Form 5472 with pro forma 1120, can be faxed to specific IRS numbers. Fax is faster than mail, but you still don’t get the same immediate confirmation as with e-file. If you fax from outside the U.S., international lines sometimes fail, and you may not know whether the IRS actually received the submission.
3. Physical mail
Some forms still require mailing. When you mail to the IRS, the postmark date is considered the official filing date, not the date the IRS receives it. This is a crucial protection—if you send your return before the deadline, it counts as timely filed even if the IRS processes it later.
However, if you mail from outside the U.S., the IRS does not always honor foreign postmarks. That means the return is considered filed only when it arrives, which can put international filers at risk of being treated as late.
Which forms can be e-filed, faxed, or mailed only
Not every tax form can be sent the same way. Here’s a simple breakdown:
- Form 1120 (corporation return): Can be e-filed or mailed. Bookmate e-files for speed and confirmation.
- Form 1065 (partnership return): Can be e-filed or mailed. E-file is strongly recommended to avoid per-partner late penalties.
- Form 5472 (with pro forma 1120): Cannot be e-filed. Must be faxed or mailed. Most common filing for foreign-owned single-member LLCs.
- Form 5471 (attached to 1120 or 1040): Filed as an attachment, so its submission method depends on the parent return.
- Form 1040-NR (individual nonresident): Can be mailed, and in some cases e-filed if software supports it, but many international cases still require mailing.
The limitation is clear: the forms most relevant to foreign-owned startups—especially 5472—are the ones that can’t be e-filed.
Why mailing from abroad is riskier
When mailing inside the U.S., the IRS honors the postmark rule—as long as the envelope is postmarked on or before the deadline, the filing is considered on time. But this protection generally does not extend to mail sent from outside the U.S. International postmarks often don’t count, meaning the IRS considers your filing date as the day it actually arrives at their service center.
This creates serious risk for foreign founders. A package mailed from Europe or Africa might take two weeks or more to arrive. Even if you sent it before the deadline, the IRS could treat it as late, and penalties can be assessed. On top of this, international mail can be lost, delayed by customs, or misrouted—all while deadlines keep ticking.
Extra risks for foreign founders
Foreign founders often underestimate how harsh the IRS penalties are for late filings. For example:
- Form 5472: $25,000 penalty per year, per form, even if your LLC had no income.
- Form 1065: $240 penalty per partner, per month, up to 12 months.
- Form 5471: $10,000 penalty per form, with escalating fines if ignored.
These penalties don’t care why you were late. Mailing delays from outside the U.S. are not a valid excuse. That’s why relying on international postage to meet deadlines is a dangerous gamble.
How Bookmate’s U.S. submission advantage works in practice
Here’s what happens when you work with Bookmate:
- Preparation: We prepare your federal returns (1120, 1065, 5472, 5471) based on clean bookkeeping and your company’s activity.
- Choosing the right channel: If the form can be e-filed, we e-file directly with the IRS for immediate confirmation. If it can only be faxed or mailed, we handle it from inside the U.S. so the U.S. postmark or fax confirmation protects you.
- Proof of filing: We keep electronic and physical proof of when the forms were submitted, so if the IRS ever questions timeliness, you’re covered.
- Follow-up: If the IRS issues a notice, we respond promptly from the U.S., avoiding weeks of lost time that often happens when notices must cross international borders.
This process removes the uncertainty and stress that foreign founders face when trying to file from abroad.
Real-world example
A founder in South Africa set up a Delaware single-member LLC. In the first year, the company had no revenue but received $25,000 of funding from the owner. This triggered the requirement to file Form 5472 with a pro forma 1120.
The founder tried mailing the forms directly from South Africa. Months later, the IRS sent a penalty notice for $25,000, claiming the forms were never received. The founder then engaged Bookmate, who re-submitted the filings by fax from the U.S. and successfully resolved the penalty.
Frequently asked questions
Do I need to mail original signatures?
Yes. The IRS generally requires signed originals or approved electronic signatures on returns. Photocopies without proper authorization can be rejected.
Can I just scan and email the forms to the IRS?
No. The IRS does not accept emailed returns.
Does certified mail or FedEx help?
Yes. Certified mail, UPS, or FedEx provide delivery tracking, but the key is still the U.S. postmark date. From abroad, these services may still not protect you from late status.
What if the IRS loses my return?
It happens. That’s why having proof of filing is essential. Bookmate maintains proof of e-filing, fax confirmation, or U.S. postmarks so that if the IRS misplaces your return, we can demonstrate that it was filed on time.
Can Bookmate help if I already got a penalty notice?
Yes. In many cases, we can re-submit filings properly and help request penalty relief when you can show reasonable cause.
Final thoughts
Submitting U.S. federal tax forms is not just about filling them out—it’s about making sure the IRS actually gets them, on time, and in the right place. The IRS accepts a U.S. postmark as proof of timely filing, but this protection often doesn’t apply when mailing from abroad.
For foreign founders, that makes international mailing risky and stressful. Working with Bookmate eliminates these problems by ensuring that your forms are filed through the correct channels, with proof of timely submission.
Each situation is unique. To learn how Bookmate can simplify your compliance, visit trybookmate.co or book a consultation today.
