As we’ve suggested in previous posts, one of the best ways to ensure your practice covers all of its ICD-10 prep work bases is to audit your processes and workflows. By doing so, you’ll identify all the ways you and your staff currently use and interact with ICD-9 codes. If you’ve done that, you’ve no doubt pinpointed one of the largest—and most obvious—ICD-9 touchpoints: your claims. Then, you probably asked yourself (or the almighty Google), “How will ICD-10 change the way I complete and submit claims for my services?” And now, here you are, on a blog post that’s going to answer that very question. (It’s like magic, right? I mean, what did we ever do without the Internet?) Here’s what you need to know about ICD-10 and your claims:

1. The current 1500 claim forms already accommodate ICD-10.

As this article explains, the most recent update to the 1500 form accounted for the transition to ICD-10. The new form—well, new-ish (the update happened a couple of years ago)—allows for the inclusion of up to 12 diagnosis codes. While you might not be hitting that maximum with ICD-9, you very well could use all of your allotted coding space with ICD-10, as many patient cases will require multiple codes to express the patient’s diagnosis in the most complete, accurate, specific way possible. This is especially true in cases involving external causes, as you can submit as many external cause codes as necessary to fully describe the patient’s situation.

2. You will still use CPT codes to denote services rendered.

While ICD-10 does include a separate set of procedure codes, healthcare professionals who currently use CPT codes for billing purposes will not use ICD-10 procedure codes. If you fall into this category, you will continue using CPT codes (e.g., 97161, 97110, and 97140) the same way you do now. However, keep in mind that you will need to update your superbills—if you use them—to include ICD-10 codes. This process is easier said than done, as there could be dozens—or even hundreds—of possible ICD-10 equivalents for a single ICD-9 code. (For step-by-step instructions on how to convert ICD-9 codes to ICD-10, check out this blog post or this video tutorial.) One last note: ICD-10 will not impact the way you currently use any CPT-related modifiers, including modifier 59 and the KX modifier.

3. You can list up to four diagnosis pointers per service line.

While you can include up to 12 diagnosis codes on a single claim form, only four of those diagnosis codes can map to a specific CPT code. That’s because the current 1500 form allows space for up to four diagnosis pointers per line, and that won’t change with the transition to ICD-10. So, why even list diagnosis codes that you’re not going to link to any of your service lines? This article answers that question using the following example: “For a service that is somewhat generic like an office visit, the patient may have come in because they had the flu, but ended up getting a full evaluation that showed a previous lower leg amputation and perhaps diabetes management. While the office visit did not address the leg specifically, capturing the diagnosis is still very important.” Furthermore, even though you can only officially point four diagnoses to any one service, if the other diagnoses “are relevant to the treatment, they are still available to the examiner at the insurance company who is doing the adjudication—they just are not specifically pointed to.”

Everything PTs, OTs, and SLPs need to know about ICD-10—in one comprehensive guide. Download your copy now.

4. If you include multiple diagnosis codes on a single claim, you should order them according to significance.

To reiterate the point I made above, with ICD-10, there will be a lot of instances in which you will submit multiple codes on a single claim. When this happens, it’s crucial that you list the codes according to importance, with the first-listed (i.e., primary) code being the one that most strongly supports the medical necessity of your services. In many cases, that means coding for causation first and foremost. For more on coding for medical necessity, check out this blog post.

5. There’s no minimum number of ICD-10 codes you must include on each claim.

Even though there’s a good chance you’ll list multiple codes on a single claim, keep in mind that there’s no requirement to submit multiple codes. Obviously, you’ll need at least one diagnosis code for the claim to process correctly, but if that one code provides all the information necessary to describe the patient’s condition as fully and specifically as possible, then it’s 100% acceptable to submit that code, and that code only.

6. ICD-9 codes and ICD-10 codes can never appear together on the same claim.

The transition to ICD-10 will go by date of service. That means all claims with dates of service on or before September 30 must contain only ICD-9 codes, whereas all claims with dates of service on or after October 1 must contain only ICD-10. Mixing the two code sets could be a recipe for disaster in the form of claim denials. So, if you need to submit a claim for dates of service that span the transition, you’ll need to split the claim to submit the ICD-9 codes and ICD-10 codes separately. Just be sure to check with your payers regarding their claim-splitting requirements.

All of that being said, you shouldn’t throw all of your ICD-9 knowledge out the window come October 1, because a handful of nontraditional, non-HIPAA-covered payers—including auto insurance and workers’ compensation carriers—are exempt from the transition mandate. And even though they are being strongly encouraged to make the switch anyway, some will definitely stick with ICD-9—at least for now. So, you’ll need to continue using ICD-9 codes on claims submitted to those payers. Furthermore, as Lauren Milligan explains in this blog post, “Sometimes, you’ll see patients whose primary and secondary insurances require different code sets. In these cases, because you should include only ICD-9 codes on claims for payers who did not make the switch to ICD-10, you’ll need to split the claim and send each piece to the appropriate payer.”

7. To be safe, you should get all caught up with claim submissions before October 1.

Because the transition is based on date of service, payers theoretically should be equipped to handle claims containing ICD-9 codes—even when those claims are submitted after October 1. However, in the event that the payers are not adequately equipped to handle that distinction, you may experience delays in payment or have to deal with appeals or claim resubmission. That’s why we’re encouraging everyone to get all caught up with their billing—or as caught up as possible—prior to October 1. (For more advice on how to approach the hours leading up to, and immediately following, the transition, check out this blog post.)


At the end of the day (specifically, the day of September 30), not much will change with respect to your actual claims and the way you complete and submit them. The real change will occur behind the scenes as you adjust your coding mindset to align with ICD-10’s call for greater accuracy, completeness, and specificity. Have claims questions? Enter them in the comment section below, and I’ll get you an answer.

Oh, and be sure to check out this PT billing FAQ for even more great advice on billing and claims submission.