Which Came First, the POS or the TOB?

Understanding the site of service for a claim is critical for understanding and interpreting medical claim data. The easiest way to assign a claim to the site of service is to use the place of service (POS) code available in the claims extract, but the POS code does not tell the entire story.

To understand how POS code is assigned to a claims extract it is necessary to review the process by which a medical claims dataset is created. In short, a provider submits a bill to a payer. The bill is then adjudicated and paid by the payer. Paid claims data is then transformed and warehoused by the payer. This warehoused data is usually the data made available to downstream vendors, providers, or state agencies.

Site of service information arrives on the bill in one of two ways: non-facility providers submit ‘professional’ claims (837p/CMS-1500) including a POS code; facility providers submit an ‘institutional’ claim (837i/UB-04) including a type of bill code. The POS code is a non-standardized code made available by the payer to the provider (this is usually the CMS two-digit code set, but can be a local version). The Uniform Billing Type of Bill (TOB) code is a standardized code set maintained by the National Uniform Billing Committee (NUBC). Both of these codes can be used to identify where the service took place.

For example:

POS code 11 – Provider Office

TOB code 11X – Inpatient Facility

Where Am I?

There are a variety of data processing issues that can (and do!) take a clear picture of where a service occurred and muddy the waters. First, the claims extract you receive may not maintain the TOB code. Sometimes, for institutional claims, the POS code will be a crosswalk of the TOB code to the payer’s POS code set. Sometimes the POS code will be a copy of the first two digits of the TOB code. Alternatively, the extract may contain the TOB code and the POS code, but each service component may not align. This occurs when the institution submits a bill with a TOB indicating one facility type and the professional provider submits a bill with a POS code indicating a different facility type.

To discover the first scenario, a quick crosstab will usually identify the issue. Consider the two summaries below:

POS with TOB Substitute

1120347.9% $                 483.14
1210.0% $                   63.00
1364143.9% $                 140.21
141644.6% $                   57.98
2270.6% $                 170.57
23110.3% $                   64.14
8170.2% $                   54.50
8332.5% $             1,696.93
Grand Total1,037100.0% $                 197.58

Original POS

111836.7% $                           78.65
1210.0% $                           63.00
211841.9% $                      4,973.44
2274042.0% $                         121.46
23566.8% $                         257.98
2432.4% $                      1,696.93
8170.2% $                           54.50
Grand Total1,008100.0% $                         212.08

Discovering the second scenario is more difficult and requires looking directly at the data. Consider the data in the FHC tool. The POS code suggests an outpatient visit, but the UB_TOB code indicates inpatient. In general it is wise to trust the UB_TOB code. As mentioned above, there is no POS code included on an institutional claim. Somewhere during the warehouse and extraction process POS code was mapped onto the facility data. Frequently this process results in errors. In this case we can see that the revenue code of ‘0120’ (Room & Board) supports the UB_TOB code.


To get the most accurate picture of where a medical service takes place it’s important to understand how the place of service code and type of bill code are used and how they are processed. Both fields are generally required for payment, but they cover two distinct event types. Type of bill data is more reliable but often lost during warehousing or extraction. Place of service is more ubiquitous but sometimes less reliable.