Frequently Asked Questions about the National Death Index

Who can use the NDI?

The NDI service is available to investigators solely for statistical purposes in public health and medical studies. The service is not accessible to organizations or the general public for legal, administrative, or genealogy purposes, etc.

Why do I have to apply for NDI data?

The NDI database contains selected Personally Identifiable Information (PII), which is used to match the researcher’s external records to the NDI. Therefore any researcher wanting to use the NDI must go through an application process and sign confidentiality documents. Then their application is vetted by an independent review board (NDI Advisors), which includes several state registrars.

How does the application process work?

The first step is to submit an application to NCHS for review. Please see our page on Applying for a Search for complete instructions on how to submit an application. Once approved, the researcher submits their data, along with payment, to the NDI.

Who reviews the applications?

Each application is reviewed by NDI Advisors to ensure that state data are protected against misuse. Advisors are a mix of state vital records and health statistics staff, as well as outside researchers and health scientists. We encourage interested jurisdiction staff to participate as Advisors to help protect the integrity of state NDI data, as it has been protected for decades.

If you are interested in becoming an NDI Advisor, please contact NDI staff at ndi@cdc.gov or by calling (301) 458-4444.

What information will I get from an NDI search?

The NDI returns to the researcher the date of death, state of death, and death certificate number for all matches. For all true matches, they also get all the cause(s) of death listed on the death certificate, in ICD format, if the researcher has purchased the NDI Plus service.

How are death records matched with user records?

Requested NDI file years are searched to determine whether a particular NDI death record qualifies as a possible record match with a particular user record.

To qualify as a possible record match, both records must satisfy at least one of seven conditions or matching criteria. See Chapter 4 of the NDI User Guide [PDF – 25 KB] for the complete list.

NDI users are encouraged to submit as many of the following data items as possible for each study subject: first and last name, middle initial, father’s surname, social security number, month, day, and year of birth, race, sex, marital status, state of residence, and state of birth.

How much will the service cost?

The fees for routine NDI searches consist of a base service charge, plus an additional fee per user record. Costs of using the NDI will vary by the type of search requested.

There are four main types of search requests:

1. ROUTINE: This request does not provide any cause of death information for results, only the fact of death information listed above. Vital status is not known by the researcher. In 2020, the cost is estimated at $0.15 per subject per year searched.
2. UNKNOWN: This request is similar to a ROUTINE search request, but is part of the NDI Plus service, and provides the cause(s) of death information. Here too, vital status is not known by the researcher. In 2020, the cost is estimated at $0.21 per subject per year searched.
3. KNOWN: This category is also part of the NDI Plus service, but in this search request the researcher knows that all the subjects are deceased. Hence the cost is higher, at a flat rate of $5.00 per subject, regardless of the number of years searched. All the same information as an UNKNOWN search is returned to the researcher.
4. CERTIFICATE: This is the least utilized category, as the researcher must already have a copy of the death certificate. They submit a search request to the NDI because they wish to obtain the ICD codes used to identify the cause(s) of death on the death certificate. As such, it too is part of the NDI Plus service. In 2020, the cost is estimated at $2.50 per subject, regardless of the years searched.

Please note that fees for the NDI Plus service are slightly higher.

Are discounts provided for large volumes?

If you are considering submitting more than 100,000 records for an NDI search, you may be eligible for our fee discounts for large record volumes.

There is a one-time volume discount available to researchers with search requests in excess of 100,000 unique subjects.   This is only valid for ROUTINE and UNKNOWN search requests and for records over the 100,000 threshold, limits the cost to two years regardless of the number of years requested for searching.

There is another volume discount which is not limited to one-time usage but reduces the fees in staggered fashion starting at the 100,000/500,000 (unique subjects per search request) threshold for KNOWN and CERTIFICATE searches.

For ROUTINE and UNKNOWN searches, there is an additional discount at a threshold of 2.5 million unique subjects.

NDI offers free duplicate records and reruns. Visit the guidance page for details.

For more information, please contact NDI staff at ndi@cdc.gov or by calling (301) 458-4444.

How do I make my payment?

The NDI accepts payments through credit cards, checks, and purchase orders. Credit card payments that do not exceed $24,999.99 can be accepted—contact NDI staff to arrange for such payments. ACH payments (these are direct withdrawals from your bank account) above the $24,999,99 ceiling can also be processed. Checks or purchase orders are not acceptable from federal agencies, but credit card payments can be accepted. We encourage federal agencies to pay via credit card if their cost is below that ceiling. Otherwise, federal agencies can also process a standard interagency agreement in advance of their NDI searches.

How do NDI payments to jurisdictions work?

The jurisdictions share in the revenue from the NDI-Plus search requests because death information is owned by the 57 reporting jurisdictions. The calculated share is not a fixed amount.

A given jurisdiction’s revenue depends on the cost of each search, as well as the jurisdiction of death for each “true match.” A true match is the one match that is likely to be the correct one for a given subject. Many matches are poor matches, and many of the researcher’s subjects may find no match.

How is NDI revenue used?

Since its inception, the NDI was designed to be self-supporting from revenue; it uses no appropriated funds. Revenue in excess of NDI operating expenses and jurisdiction revenue shares are used to support mortality improvement projects. It also provides supplemental funds to NAPHSIS and to improve the National Vital Statistics System.