T21.40XS — Corrosion of unspecified degree of trunk, unspecified site, sequela

BillableUnspecified

Is T21.40XS billable?

Yes, but T21.40XS is an unspecified code. T21.40XS is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, T21.40XS is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting T21.40XS — the more specific alternatives are listed below.

More specific alternatives

T21.40XS at a glance

Code	T21.40XS
Description	Corrosion of unspecified degree of trunk, unspecified site, sequela
Billable	Yes
Code set	ICD-10-CM FY2027
Valid for encounters	October 1, 2026 – September 30, 2027
7th character "S"	sequela

What does the 7th character "S" mean in T21.40XS?

In T21.40XS, the 7th character S means sequela. The 7th character is required for T21.40XS to be a valid, complete code.

Same condition, different episode of care — switch the 7th character:

Which MS-DRGs does T21.40XS group to?

T21.40XS sits in MDC 09 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.

604Trauma to the Skin, Subcutaneous Tissue and Breast with MCCmedical
605Trauma to the Skin, Subcutaneous Tissue and Breast without MCCmedical

How is T21.40XS listed in the Alphabetic Index?

The Alphabetic Index lists these routes under T21.40, the nearest indexed parent of T21.40XS. Use them to find the family, then select the specific code.

Corrosion › trunk (injury) (acid) (caustic) (chemical) (lime) (external) (internal)

Code first — inherited from T21.4

The underlying condition below must be sequenced before T21.40XS. T21.40XS describes a manifestation and cannot be the principal or first-listed diagnosis.

(T51-T65) to identify chemical and intent

Use additional code — inherited from Chapter 19

Report an additional code alongside T21.40XS to fully describe the condition. T21.40XS is sequenced first.

code to identify any retained foreign body, if applicable (Z18.-)

Use additional code — inherited from T20-T25

Report an additional code alongside T21.40XS to fully describe the condition. T21.40XS is sequenced first.

code from category T31 or T32 to identify extent of body surface involved

Use additional code — inherited from T21.4

Report an additional code alongside T21.40XS to fully describe the condition. T21.40XS is sequenced first.

external cause code to identify place (Y92)

Excludes2 — not included here — inherited from Chapter 19

The conditions below are not part of T21.40XS, but a patient may have both at the same time. When documentation supports it, T21.40XS and the excluded code may both be reported.

birth trauma (P10-P15)
obstetric trauma (O70-O71)

Excludes2 — not included here — inherited from T21

The conditions below are not part of T21.40XS, but a patient may have both at the same time. When documentation supports it, T21.40XS and the excluded code may both be reported.

burns and corrosion of axilla (T22.- with fifth character 4)
burns and corrosion of scapular region (T22.- with fifth character 6)
burns and corrosion of shoulder (T22.- with fifth character 5)

How long has T21.40XS existed?

T21.40XS has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.

Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.