TC 340: Restricted Interest Assessment

What the code actually does

TC 340 posts manually computed underpayment interest. IRS Document 6209, Section 8A titles it “Restricted Interest Assessment” and defines it in one sentence — “restricted interest which must be manually computed” — then adds a caution that is the whole practical story of the code: “After posting, interest is not computed or abated by computer for the applicable Tax Module and assessed interest thereafter must be computed manually and input with a TC 340 or 341.” The word doing the work is *restricted*. A normal module has Master File computing interest continuously in the background; a restricted module has that turned off, and every later interest figure on it is somebody’s arithmetic rather than the system’s.

Two generators are worth recognising because they produce a TC 340 nobody decided to input. Doc 6209 records that a TC 500 generates a TC 340, and that a return posted with Condition Code Z “generates TC 340 for zero amount, turns on debit restricted interest indicator and restricted FTP penalty indicator.” A zero-dollar TC 340 is therefore not a clerical oddity — it is the flag that says this module has stopped computing on its own.

Why the IRS did it by hand at all

Manual interest is the exception, not the routine, and the IRM says so as policy: IRM 20.2.1.4.1 instructs employees to “allow IRS computer systems to systemically calculate interest whenever possible.” A TC 340 therefore means the module hit something Master File cannot handle. IRM 20.2.5.6.1 lists those situations, and the list is a useful diagnostic on its own: carryback adjustments computed on Form 2285, combat-zone service with multiple tours inside a six-month window, federally declared disaster areas, estate tax returns, foreign tax credit adjustments, employment tax cases with an IRC 6205 ascertained date, large corporate underpayments, modules carrying an expired collection statute, and credit reversals with a pre-July-2015 interest suspension period. If a client’s module carries a TC 340, one of those is almost certainly the reason, and identifying which one tells a practitioner what the computation was supposed to account for.

The same code that does not restrict anything

This is the part most summaries of TC 340 get wrong, and it matters because it changes what a practitioner should expect the module to do next. A TC 340 does not necessarily restrict. IRM 20.2.5.6.3 describes the non-restricting TC 340 as “an enhancement to Master File programming to allow a systemic interest update on a tax module after interest has been manually computed,” and says plainly that it “should be used whenever possible.” Mechanically, the employee enters the total balance including accruals in the COMP-INT-AMT field, “which causes Master File to resume normal interest computation on that amount” from the date entered in the DB-INT-TO-DT field. The IRM directs it at exactly the recurring cases — multiple waiver dates, carryback combination adjustments, disaster areas, abatements for a ministerial or managerial delay, combat zone participants, and removing a large corporate underpayment trigger date that should not apply. So the honest reading of a TC 340 is: interest was computed by hand, and whether the computer picked the module back up afterwards is a separate question the transcript does not answer on its face.

Why the figure is a number to check, not a number to accept

A restricted interest amount is the output of a human computation performed under time pressure against one of the hardest rule sets in the Code, and the IRS’s own quality controls around it are lighter than most practitioners assume. IRM 20.2.5.6.2 asks all personnel to review their own computation, and then says a review by a second technician with interest expertise is “recommended” only once the computation exceeds $100,000 per tax module — a recommendation, with local management free to lower the threshold but not required to. Everything below that rests on self-review plus “random quality reviews.” That is not an accusation of carelessness; it is a description of a control environment in which an error can survive to the transcript.

The practitioner’s leverage is that the computation exists as a document. The same subsection requires the employee to “always attach the computation and the reason for the action taken to the adjustment source document,” and to state the reason in the remarks whenever interest is abated or a zero-amount TC 340 is input. A restricted interest figure a client cannot explain is therefore a figure with a retrievable paper trail behind it, and asking for it is a normal request rather than an escalation. What will not work is arguing the equities: IRM 20.2.1.4.1 forecloses that in a single line — “there is no provision in the law permitting interest to be adjusted for reasonable cause.” Restricted interest is challenged by recomputing it, not by explaining the client’s circumstances.

What TC 340 gets confused with

TC 340 gets confused with TC 336, because both post interest on a module that has just been adjusted and both can appear alongside an examination assessment. They are opposite in kind: TC 336 is a generated transaction, computer-assessed interest on a deficiency when an exam adjustment posts, and it leaves the module computing normally. TC 340 is the manual figure, and it can switch that computation off. Reading a TC 340 as though it were a TC 336 means treating a hand-built number as a systemic one and never asking for the workpaper.

It also gets read as interchangeable with its own reversal, TC 341, on the theory that a 340 adds interest and a 341 removes it and the pair nets out. The netting is real but the restriction is not symmetrical in the way that suggests: both codes carry the same caution about the module no longer computing, so a TC 341 does not undo the restricted state a TC 340 created. Only TC 342 does that, and it has its own preconditions.

The practitioner’s actual next step

Establish which of the manual-computation triggers applies before doing anything else — the reason for the restriction determines what a correct computation would have looked like, and it is usually visible in the surrounding transactions on the module.

Request the computation. It is required to be attached to the adjustment source document, so a figure the client cannot reconstruct is a figure the IRS can be asked to produce rather than one to be inferred.

Recompute independently before disputing anything. Interest is not abatable for reasonable cause, so the only viable challenge is an arithmetic or date error — which means the argument has to be a competing computation, not a narrative.

Check whether the module is still restricted or was picked back up by a non-restricting TC 340, because that determines whether later accruals on the account are systemic or will keep arriving by hand.

Pull the full transaction history with the IRS Transcript Decoder before advising on a payoff figure — on a restricted module the balance a client is quoted and the balance the module actually supports can diverge, and a payoff quoted from a stale manual computation is the most common way that gap reaches a client.