Is an out of state LLC required to register in the state if they have business dealings in OK? We have a Delaware LLC that has their business office in OK and deposit accounts and loans with the bank.

It depends on whether the LLC's activities constitute doing business in the state:

Title 18, Section 2049
A. The following activities of a foreign limited liability company, among others, do not constitute transacting business
within the meaning of this act:
1. Maintaining, defending, or settling any proceeding;
2. Holding meetings of its members or carrying on any other activities concerning its internal affairs;
3. Maintaining bank accounts;
4. Maintaining offices or agencies for the transfer, exchange and registration of the foreign limited liability
company's own securities or maintaining trustees or depositaries with respect to those securities;
5. Selling through independent contractors;
6. Soliciting or obtaining orders, whether by mail or through employees or agents or otherwise, if the orders
require acceptance outside this state before they become contracts;
7. Creating or acquiring indebtedness, mortgages and security interests in real or personal property;
8. Securing or collecting debts or enforcing mortgages and security interest in property securing the debts;
9. Holding, protecting, renting, maintaining and operating real or personal property in this state so acquired;
10. Selling or transferring title to property in this state to any person; or
11. Conducting an isolated transaction that is completed within thirty (30) days and that is not one in the course
of repeated transactions of a like nature.

Without knowing what the LLC does, I cannot advise whether registration is required.