Vivarium Per-Diem Billing Best Practices
Per-diem billing is the standard cost-recovery mechanism for academic and institutional vivaria. Key principles:
Rate setting: Per-diem rates should cover direct costs (bedding, feed, water, cage wash labor, veterinary oversight) plus facility overhead (utilities, equipment depreciation, administrative staff). NIH requires that federally funded animal facilities use rates that do not generate surplus beyond what is needed for operations.
Billing frequency: Monthly billing is standard. Some facilities bill quarterly. The billing period should align with your institution's accounting cycles. Mid-month transfers (cages moving between PIs) are typically prorated or billed to the PI who held the cages on a census date.
Volume discounts: Some facilities offer tiered pricing to encourage efficient colony management. PIs with larger colonies benefit from economies of scale in cage processing. Discounts are typically 5–15% for high-volume users.
Fund code tracking: Each PI may have multiple funding sources (R01, P01, departmental funds). Accurate fund code assignment ensures proper cost allocation and compliance with grant terms.