You hit submit on your return. Here is what happens on the other end

Most people's understanding of the tax system ends at the moment they file. That is the point at which a return enters a processing pipeline that runs on its own schedule, applies a sequence of automated checks, and can produce correspondence months later that arrives with no context. Knowing the shape of that pipeline turns a letter from an alarming event into a routine one, which is worth a fair amount on its own.

Here is the sequence, in the order it happens.

Acceptance is not processing

An electronically filed return is first checked for structural validity: does the identifying information match, is the return internally consistent, has a return already been filed under this Social Security number. That check happens quickly, often within a day, and produces an acceptance or a rejection.

Acceptance means only that the return has been received in a readable state. It says nothing about whether the numbers are right. Rejection is usually mechanical and fixable: a mistyped identification number, a name that does not match the record, or a dependent already claimed on another return. The last of those is worth pausing on, because a rejection for a duplicate filing is frequently the first sign that someone has filed fraudulently using your details.

A paper return skips this step entirely and goes into a queue to be handled manually, which is why the timeline for paper filing runs longer by a wide margin.

Processing, and the refund timetable

The return is then processed: figures are validated against the information returns already on file, credits are checked against eligibility rules, and the balance or refund is finalized. For a straightforward electronically filed return with direct deposit, refunds usually issue within a few weeks.

Certain credits carry a statutory hold that delays refunds for returns claiming them until a set date, regardless of when the return was filed. This surprises people every year. It is not a sign of a problem and there is nothing to be done about it.

Returns that require manual review take longer, sometimes considerably longer, and the review is often triggered by something dull: a figure that does not match an information return, a first year claiming a particular credit, or an amended return in the queue ahead of it.

The letters, and what each kind means

Correspondence falls into recognizable categories and the differences matter.

• A math error notice. An arithmetic or transcription discrepancy was found and corrected, and the balance or refund has been adjusted. You have a limited window to disagree, and after it closes the adjustment stands.
• An underreporter notice. The figures reported to the agency by third parties do not match what you reported. This is a proposal, not a bill, and it is frequently wrong in your favor because it may not account for a cost basis or an offsetting item. It requires a response either way.
• An identity verification letter. The return has been held pending confirmation that you filed it. Respond through the specified channel promptly; the return does not move until you do.
• An examination letter. An actual audit, which most commonly means a correspondence audit asking for documentation of one or two specific items rather than anything resembling the version in films.

The consistent advice across all four is the same: respond by the date on the letter, in writing, keeping a copy and proof of delivery. Ignoring a proposal turns it into an assessment, and unwinding an assessment is much harder than answering a proposal.

Amending, and when it is worth it

If you find an error yourself, an amended return corrects it. It is a separate form, it generally has to be filed on paper or through specific electronic channels, and it takes months rather than weeks to process. Filing one is not an admission of anything and it is not unusual.

There is a deadline for claiming an additional refund through an amendment, generally measured from the original filing date or the date the tax was paid, whichever is later. If an amendment would produce money back, check that window before deciding it is not worth the trouble, because the trouble is a couple of hours and the window does close.

What does not require an amendment: an arithmetic error the agency has already corrected, or a missing form the agency has already asked you for. Answer the letter instead. Filing an amended return in parallel with a correspondence process creates two threads about one issue and slows both.

How long to keep everything

The general assessment window runs three years from filing, extending to six where income is substantially understated, with no limit at all where no return was filed. That structure is the basis for the common advice to keep returns and supporting records for at least three years and preferably longer.

Some records outlive that window because they establish a figure used later. Purchase documents for a house, records of improvements, basis records for investments, and anything documenting a retirement account contribution should be kept until the asset is sold and the return reporting that sale is itself out of its window. None of these periods is arbitrary. Each one is tied to how long the IRS still has to question the return a record supports, which is also why the clock runs from the date the return was filed rather than from the date on the receipt.

Scan and keep two copies, one of them somewhere a flood or a fire at your house cannot reach.

What to do the week after you file

Three small things make the following twelve months easier. Save a complete copy of the return as filed, including every schedule, because next year's software will ask for figures from it. Note the refund or balance due and check that it actually arrives or clears. And if you owed more than you expected, adjust the coming year's withholding or estimated payments now rather than in December, while the reason is still fresh.

The pipeline runs whether you watch it or not. Watching it for a week costs almost nothing, and it catches the two problems that are genuinely worth catching early: a return filed by somebody else, and a payment that never landed.