Purpose of loan is to purchase a medical office building in "A" Census Tract.

Primary collateral is medical office building in "B" Census Tract.

Which address do I use for CRA Reporting?

Whichever tract is LMI.

The reporting address is to be the main business address or the collateral address per reporting instructions. A bank needs to have a policy to do this fairly consistently. You are not expected to pick and choose loan by loan.

Thanks Kathleen....so what address do I use? Oh by the way, the corporate HQ is in Census Tract "C".

You choose, but I should clarify while responding. What the guidance states is use headquarters or address where proceeds will be used (which often will match the collateral, but not always.)

From the Q and A:

"Many borrowers have street addresses
in addition to rural route and box
numbers. Institutions should ask their
borrowers to provide the street address
of the main business facility or farm or
the location where the loan proceeds
otherwise will be applied."

Also:

§ll.42(a)(3)—1: Which location
should an institution record if a small
business loan’s proceeds are used in a
variety of locations?

A1. The institution should record the
loan location by either the location of
the small business borrower’s
headquarters or the location where the
greatest portion of the proceeds are
applied, as indicated by the borrower.

Yes, it often is referred to as the collateral address because often when there is a different address, it happens to be collateral being purchased with the proceeds, but it really is a "proceeds address".

Is there a guide to tell you what tract to use in different scenario's? Newbie here.

The CRA guide and Q and A are available at the FFIEC CRA website.