- Do not wait for 15 April to hurry
- Four key dates on the filing calendar
- Collect vouchers first, then compute
- Different company types, different forms
- Three filing routes, which suits you
- Real cases: three companies, three routes
- Common muddles in the filing process
- Frequently asked questions on the filing process
Every March and April my WeChat gets busy with US company owner groups, all asking the same thing: how the US company tax filing process actually works. Someone registered last year, received the first IRS letter this year and panicked; someone paid on time and was still fined, feeling wronged; someone simply deleted the email and looked away, with penalties rolling up. Today no textbook: following the habits of a twenty-year cross-border tax hand, I will break the process down into usable pieces.
Do not wait for 15 April to hurry
The first step of the US company tax filing process actually happens three months before you file, or earlier. Why? Because US filing follows identity: you do not compute money first but fix identity first. A registered LLC may by default be treated as a pass-through entity with income merged into the shareholder's personal return; a C-Corp is a separate taxable entity filing Form 1120; S-Corps and partnerships each play their own game. Get this wrong and everything downstream is wrong, so the first task is to know which identity your company has before discussing steps.
Four key dates on the filing calendar
Broken down, filing means carving the dates into your brain. For companies with a calendar accounting year, 15 March is the deadline for S-Corp and partnership forms, 15 April for individual tax and C-Corp forms, 15 June the extension date for overseas residents, and 15 October the final deadline after extension for most entities. Many watch only 15 April, and 15 March for S-Corps passes unnoticed with a penalty added. My long-term clients share one habit: at the start of filing season they stick these dates on the computer screen, better than an alarm clock.
Collect vouchers first, then compute
By the stage of computing tax, what matters is your normal bookkeeping. The IRS does not require daily bookkeeping but requires figures with basis. Bank statements, receipts, contracts, depreciation schedules and payroll records form the evidence chain. I knew a young e-commerce owner whose annual receipts all went through PayPal; diligent enough, but with no classification of which order each payment matched, he spent half a month digging through the backend to assemble them at filing. Hard work, but at least there was something to dig; the real fear is not even being able to log in, leaving only bank statements to force-match.
A tip: file vouchers into five baskets - revenue, cost, expenses, assets and loans - each by month. At filing, whatever the accountant wants, you find in three minutes. A hidden benefit: if the IRS ever spot checks, you can produce complete matching records, killing many problems at the source. Do not underestimate this habit; I have seen too many clients turn an uncomplicated matter into a disaster in the state of cannot find what is needed.
Different company types, different forms
Form selection is where ignorance easily causes failure. C-Corps file Form 1120, S-Corps Form 1120-S, partnerships Form 1065, single-member LLCs usually merge into the individual Form 1040, and employers also have Form 941 and the W-2 series. Many ask: my LLC is registered in Wyoming and I am in Shenzhen, which type is it? That requires going back to the operating agreement and default tax classification. If no S-Corp election was made at registration, the LLC likely follows the default pass-through rule. Settle these first, then discuss which form to fill; the order cannot be reversed.
Three filing routes, which suits you
Knowing what tax and when, next is how. Three common routes: self-filing with software, a local US accountant, or a Chinese cross-border tax team end to end. Self-filing is cheapest but requires understanding the forms, otherwise K-1 and Schedule C alone are daunting; a local accountant is professional but has time differences and higher quotes; a domestic team knows Chinese clients' business structure and can clarify the basis between domestic income and the overseas entity. No route is absolutely better; it depends on complexity. The table below is what I usually show clients.
| Dimension | Software self-filing | Local US accountant | Domestic cross-border team |
| Suitable for | Very simple new companies | Mainly US local business | Cross-border business in both countries |
| Fee range | Tens to hundreds of USD | Hundreds to over a thousand USD | From thousands of RMB by complexity |
| Communication | Immediate, self-reliant | Time difference, email exchanges | Same language, anytime |
| Risk | Misreading the forms | Misunderstanding domestic business logic | Must verify qualifications and scope |
Real cases: three companies, three routes
Case one, Mr Liu in Guangzhou running an independent store registered a California LLC with no US employees or office in the first year, only marketplace sales revenue. He first wanted to self-file and was baffled by Schedule C and self-employment tax. We confirmed the LLC pass-through identity, gathered revenue, platform commissions, advertising and sample costs item by item, and after filing also estimated next quarter's prepayment so he knew where he stood. He later reported that understanding filing improved his sleep.
Case two, Mr Zhou in Shenzhen ran a Delaware C-Corp whose equity structure became complex after financing, involving parent-subsidiary related-party transactions. That size cannot be held by software alone. We arranged two teams: domestic staff organised related-party documents and transfer pricing explanations, the US partner accounting firm issued the filing materials, and the whole took over a month, completed before the extension date. He calculated that although the service fee was a few thousand USD, a misreport under inspection could multiply interest and penalties several times over; the money was worth it.
Case three, Mr Lin in Hangzhou running overseas warehouse business had a Wyoming LLC with shareholders in China and no revenue in the first year, only registration and annual fees. The pitfall for such idle companies is assuming no revenue means no filing, then being penalised for missing it. We filed the return normally under zero income and zero tax rules; the cost was low but the compliance record was preserved. He said had he known it was this simple, he would not have listened to friends saying just leave it.
A fourth case, Mr He in software outsourcing registered in Delaware with the development team in Chengdu and half the revenue from US clients. His trouble was not filing itself but foreign income recognition and double taxation concerns. We reviewed the permanent establishment clauses in the China-US tax treaty, confirmed he had no physical presence in the US, worked with a tax adviser on an explanation, then handled the US filing basis reasonably while keeping the Chinese tax payment certificates, so both sides' books matched. Mr He later told me that both sides taxing is not necessarily true; it depends on how the structure is built.
Common muddles in the filing process
Errors when computing tax concentrate in three areas: depreciation, since whether office equipment, vehicles and software can be depreciated and over how many years directly affects the year's cost; the relationship between state and federal tax, since federal rules differ from California, Texas and New York state bases, and many clients think federal filing ends it and then face state recovery; and estimated tax, since the IRS requires quarterly prepayment when expected underpayment exceeds a threshold, with interest and penalties for missing it. These details are where professional and amateur filing part ways.
| Common mistake | Consequence | Correct approach |
| Treating an LLC as a corporation | Extra self-employment tax, scrambled filing structure | Confirm pass-through identity before choosing forms |
| Federal tax only | State tax missed, state recovery | Check obligations in registration and operating states |
| Ignoring quarterly prepayment | Interest and penalties on top-up | Estimate from last year's burden and prepay quarterly |
| Treating extension as exemption | Extension buys time, not tax relief | Pay estimated tax in full before extending |
Frequently asked questions on the filing process
Must I file with no revenue? - Yes; most states require LLCs to submit annual filings even with zero revenue, and missing them brings penalties or dissolution. What is a pass-through entity? - The company itself pays no income tax and profit passes through to shareholders' personal returns; LLCs and S-Corps mostly fall here by default. How long can an extension last? - Form extensions are generally six months, but tax cannot be delayed; late payment brings interest and penalties. Can a wrong filing be corrected? - Yes; submit an amended return as soon as the error is found before the deadline, and the earlier the smaller the loss. Do rates change under the new administration? - Rates change yearly; rely on the current year's official IRS forms and guidance and distrust old forwarded versions online. Who should I trust for a first filing? - First check whether they understand Chinese cross-border business structures, then verify qualifications and cases; do not compare only prices.
The US company tax filing process comes down to four steps: fix identity, watch dates, collect vouchers and compute correctly. None is hard; doing all at once is. If you are staring at an IRS letter in your inbox, or your company is in its first year and you are unsure which taxes apply, send me your company type and a brief business summary and I will walk through the process with you and see where you are stuck.
