Billing

The Stable Isotope Facility (SIF) will be closing, effective July 26, 2026.

June 3, 2026
An Update on the Plant Sciences Stable Isotope Facility

Dear Faculty, Staff, Students, and Supporters,
After a lengthy review process and careful consideration, we have made the difficult decision to sunset the Stable Isotope Facility (SIF) in its current form, effective July 26, 2026.

The Department of Plant Sciences continues to face hard decisions surrounding funding allocation given the campus-wide request to reduce budgets. Over the past several years SIF has been operating with a significant and growing deficit and, despite extensive efforts over the last several months to find a solution that would allow the facility to continue to provide services to the research community, we have not found a model that is financially sustainable.

I want to thank SIF’s staff for their excellent work and dedication these past 25 years, and everyone who has played a role in supporting this facility.

We are committed to doing our best to support the researchers who rely on the facility during this transition, and will be in touch with individual clients about details of specific plans for handling existing orders over the next several weeks.

Sincerely,
Daniel Potter
Professor and Chair, Department of Plant Sciences
University of California, Davis

Original Letter

Returning SIF Samples (Facility closes July 26, 2026)

Dear Valued Client, 

After a lengthy review process and careful consideration, we have made the difficult decision to sunset the Stable Isotope Facility (SIF) in its current form, effective July 26, 2026.

The Department of Plant Sciences continues to face hard decisions surrounding funding allocation given the campus-wide request to reduce budgets. Over the past several years, SIF has been operating with a significant and growing deficit and, despite extensive efforts over the last several months to find a solution that would allow the facility to continue to provide services to the research community, we have not found a model that is financially sustainable.

We regret to inform you that SIF staff will be unable to process your submitted samples before the facility's closure date. As a result, we would like to offer the option of returning your samples. If you would like your samples returned, please submit the request via return form on the SIF website.   If you do not wish to have the samples returned, please notify us, and we will arrange for their appropriate disposal in accordance with established protocols.

We sincerely appreciate your support of the Stable Isotope Facility and the opportunity to have served your research needs.

Sincerely,
Daniel Potter
Professor and Chair, Department of Plant Sciences
University of California, Davis

As of May 20, 2026 - the Stable Isotope Facility is not currently accepting new orders. Please contact [email protected] with any questions.

Billing Questions:
Contact: Katie McCarty
E-mail: [email protected]
Phone: 1-530-752-8100 (AR is handled hybrid-remotely, communication by email is preferred)

Billing Process Overview:

  1. Review sample preparation requirements for the relevant analyses on our website prior to placing your order. Orders are placed through our client-management system, PPMS; detailed sample submission and order placement instructions can be found here. If your administration requires a Purchase Order, you may also request an estimate through PPMS once a user account has been created. The final accuracy of estimates cannot be guaranteed without verification by SIF. For verification of estimated service fees, please email us a PDF copy of your PPMS-generated estimate along with a detailed description of sample materials, including source and enrichment (if applicable).
  2. The PPMS will issue a confirmation email upon receipt of samples. After the sample analysis is complete, and during data processing, a draft invoice will be delivered from PPMS.
  3. Data will be released upon receipt of proof of payment, which may include a validated purchase order, EFT transaction receipt, or credit card payment receipt.

The SIF's invoice process requires payment for services rendered before data files are delivered. This change was initiated several years ago to reduce overhead costs associated with SIF accounting services in relation to payment collection and delinquent accounts. This has had no impact to turnaround times in most cases, does not affect how sample charges are calculated, nor our ability to address any client concerns.  We thank you for your understanding - we appreciate your business.

Vocabulary:

Order Forms are generated through PPMS and hard copies (PDF) are required to be included in sample shipments to the SIF, not only to identify your shipment of samples, but to provide confirmation of your order. Data are reported to the Researcher and PI addresses you provide on the Order Forms. If any notes are required (e.g. sample return, special payment instructions, etc.), please expand the “Comments” box prior to printing your PDF so that it is visible in the hard copy.

Purchase orders (PO) may be required by your university / institution in order to 1) establish the terms of the services you are requesting from the SIF and 2) to authorize and allocate funds to pay for services rendered by the SIF. Contact your accounting department to determine if a purchase order is necessary. Purchase orders should be emailed to [email protected] (cc: [email protected]).

Estimates / Quotes may be requested by clients to establish a budget, generate a purchase order, or allocate funds with their funding agency. Estimates/quotes are not invoices. We do not issue Proforma Invoices for prepayment. The prices listed on each of our Analytical Services pages can be used for quick budgeting, but are subject to change, and incidental fees may be incurred at time of analysis. Please email your Estimate/Quote request with sample details to [email protected].

Invoices are typically generated after samples have been analyzed, prior to data reporting. Invoices are automatically e-mailed as pdf attachments from [email protected]. If you have questions regarding your invoice please contact us at [email protected].

Clients can request to be invoiced ahead of their sample analysis, however, in the event of poor/lost data, refunds may be difficult to process. Instead, we prefer to rerun the samples or apply the credit towards future sample analysis.

Invoices are payable upon receipt. You may receive a past due notice if payment is not received within 60 days of invoice delivery. Delinquent accounts over 241 days old shall have a HOLD placed on the account, suspending further sample analysis until the balance is paid.

Payment by check: (i.e. personal check, cashier's check, money order) Please include your customer number and invoice number on your check. Payments missing this information may be returned minus a fee.

Make checks payable to: The Regents of the U.C.

Mail payment to: UC Davis AR Lockbox, P.O. Box 741816, Los Angeles, CA 90074-1816

Payment by bank wire transfer: Please e-mail to request our bank information or to inform the SIF of payment details. Multiple invoices can be combined into one wire transfer, but please remember to include the invoice number(s), otherwise payment may be returned minus a fee. EFT fees should be paid by the payer in addition to the invoice balance due.

Payment by credit card: The SIF prefers payment by credit card. Your invoice will include a link and instructions on how to pay via our secure credit card payment website. DO NOT SEND ANY CREDIT CARD INFORMATION via e-mail, phone, fax, letter, or Analysis Order Form to the SIF. To maintain security of your personal information, SIF staff are NOT allowed to handle credit card information.

University of California Researchers: University of California researchers should pay by FAU or recharge account to receive the discounted UC rate. UC clients (not including Davis campus) will receive their bill in the form of an Intercampus Order form (IOC). The IOC must be returned to [email protected] before the 20th of each month to complete the funds transfer for that month's ledger. If you have a spending deadline, please notify us 1-month in advance.

Records Retention: The SIF keeps all submitted paperwork and invoices for 3 years minimum, 6 years maximum. Do not send your only copy of any paperwork to the SIF, always retain a copy for your records. E-files of data, sample lists, and invoices are backed-up and retained indefinitely. If you lose your weight sheets or your data files, we can help you! Request Lost Data/Paperwork.