Welcome to Security First Bank
We are pleased to welcome you to Security First Bank. Your accounts will transition to us on Friday, April 10, 2026 and it is our priority to make your account transition smooth, transparent, and well supported.
This page outlines important information about key dates, what to expect, and provides downloadable versions of our Welcome Guide and Account Agreements and Disclosures.
Preparing for Change
Access your Welcome Guide and Account Agreements and Disclosures here.
Security First Bank Routing Number
104113819
You will need this routing number for new direct deposits, automatic payments,
wire transfers, and other electronic transactions beginning April 13.
What You Need to Do
Before April 10
- Verify First Interstate Bank has your current mailing address and phone number
- Write down your First Interstate Bank username
- Download or print 12-24 months of account statements or history
- Schedule Bill Payments by April 5
- Note any automatic payments tied to your debit card
- Plan ahead for debit card and ATM interruptions
- Withdraw any cash needed for the weekend
- Update your Quicken/Quickbooks information
On or After April 13
- Log in to Security First Bank Online Banking
- Download the Security First Bank mobile app
- Activate and begin using your new debit card
- Re-enroll in Electronic Statements and Account Alerts
- Update your routing number (104113819) with employers & payment providers
- Confirm scheduled transfers and recurring payments
- Begin using your new Security First Bank checks
Important Dates
Friday, April 10
- Branch Lobbies: Close at 12:00 pm local time.
All branch locations will remain closed throughout the weekend - Drive-Up Services: Close at 3:00pm local time
- Online & Mobile Banking: Unavailable after 11:00 pm MT.
- Debit Cards: First Interstate Bank debit cards stop working
- ATMs: Go offline and may remain unavailable for up to two weeks
Monday, April 13
- Branches Reopen: Normal business hours resume
- Online & Mobile Banking: Access resumes at 9:00 am MT
- Debit Cards: Activate and begin using your new
Security First Bank debit card
We're Here to Help
Our branch teams and support staff are committed to making your transition clear and well supported. If you have questions, visit your local branch or contact us at:
General Banking Assistance
877-747-3139
Monday–Friday | 8:00 am–4:30 pm MT
Online & Mobile Banking Support
844-277-8860
Monday–Friday | 6:30 am–5:00 pm MT
Download the Security First Bank Mobile Banking App
Download the App before April 13 to access your accounts without interruption.
Personal Mobile Banking App
Business Mobile Banking App
Frequently Asked Questions
Transition weekend is Friday, April 10 through Monday, April 13, 2026.
Yes. Your deposit accounts, loans, and safe deposit boxes will automatically transfer to Security First Bank. Most account numbers will remain the same unless you are notified otherwise.
Security First Bank’s routing number is 104113819.
Most account numbers will remain the same. If your account number is changing, you will receive a separate notification by mail with your new account details.
Branches will close early on Friday, April 10 and will reopen during normal business hours on Monday, April 13.
No. Online and Mobile Banking will be unavailable from Friday, April 10 at 11:00 p.m. MT until Monday, April 13 at 9:00 a.m. MT.
Debit cards will not be available from April 10 through the morning of April 13.
ATMs will go offline beginning April 10 and may remain unavailable for up to two weeks while new machines are installed and configured. We recommend withdrawing any needed cash before April 10. You may use your First Interstate Bank checks for purchases or payments over the weekend.
Yes. You will receive a new Security First Bank debit card with a new card number and PIN. Activate and begin using your new card on April 13. If you do not receive your new Security First Bank debit card prior to Monday, April 13, please visit your local branch to have a debit card printed on-site.
No. Your interest rate, payment amount, maturity date, and other loan terms remain the same. However, your loan account number will change. You will receive a letter via postal mail prior to April 10 with your new loan account number.
Yes. Loans currently set up for automatic payments will continue without interruption.
Yes. Business customers will transition to CorpLink Business Online Banking and will be contacted to schedule a required training session prior to April 10.