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N343 Remark Code: TENS Trial Start Date Missing/Invalid

N343 means the start date of the patient's Transcutaneous Electrical Nerve Stimulator (TENS) trial was missing, incomplete, or invalid, so the payer could not confirm when the trial period began.

Quick facts

Code
N343 (RARC N343)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The TENS claim was denied because the trial start date could not be validated. The supplier corrects it; the patient is not billed for this adjustment.
Official description
Missing/incomplete/invalid Transcutaneous Electrical Nerve Stimulator (TENS) trial start date.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N343 means

A TENS unit is usually tried before it is bought. Payers that cover the device tend to require a rental trial so the practitioner can document whether it helps. N343 is sent when the date that trial began was absent, incomplete, or inconsistent with other dates on the claim.

N343 most often sits on a purchase claim that comes after the trial, alongside CARC 16. If the payer concludes the trial didn’t meet its rules, CARC 108 may follow.

Common causes

  • The purchase claim was sent without any trial dates, even though the payer requires them.
  • The date the order was written was used instead of the date the patient started using the device.
  • The start date is after the end date, or after the purchase date.
  • The trial was supplied by a different company and its dates never reached the billing supplier.

Correcting the claim

  1. Find the delivery ticket or rental record for the trial device and confirm the first day of use.
  2. Confirm the ordering practitioner documented the trial results, since payers usually want evidence the device helped.
  3. Report the start date in the location the payer requires. DME payers often ask for it in narrative or supplemental fields, so read the billing article for TENS.
  4. Check that the end date (see N344) is present too, since the two are reviewed together.
  5. Resubmit as a corrected claim with frequency code 7 and the original claim number.

How to prevent it

Treat the trial as its own documented episode: log the start date at delivery, schedule a follow-up with the practitioner before the trial ends, and do not release a purchase claim until both dates and the practitioner’s assessment are on file.

Codes that may appear with N343

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Claim information is missing; N343 names the TENS trial start date.
  • CO-108 (Rent/purchase guidelines were not met.): Rent or purchase guidelines were not met, which can follow when trial dates do not support a purchase.
  • N344 (Missing/incomplete/invalid Transcutaneous Electrical Nerve Stimulator (TENS) trial end date.): The companion code for a missing or invalid TENS trial end date.
  • N331 (Missing/incomplete/invalid physician order date.): Covers a missing or invalid physician order date for the device.
  • N370 (Billing exceeds the rental months covered/approved by the payer.): Used when billing exceeds the rental months the payer approved.

N343 FAQ

Why is a TENS trial start date needed?

Payers that cover TENS often require a trial rental before purchase. The start date marks when that trial began so the payer can check its length and whether it came before the purchase.

What is the right start date?

It is generally the date the patient began using the rented device, which is usually the delivery date. Check the payer's policy if it defines the date differently.

Is TENS covered for every condition?

No. Coverage depends on the payer and the diagnosis, and some payers limit or exclude TENS for certain conditions. Check the policy before dispensing.