How to Automate amortization of pre‑paid invoices by service period (derived from PR/PO)

How to Automate amortization of pre‑paid invoices by service period (derived from PR/PO) without AP manual-

There are recurring cases where we prepay for annual services at the start of the year. The PR, PO, Invoice, and Payment are for the full annual amount.
Today, our AP team manually splits the single invoice into monthly expense recognition (amortization). This manual process is error‑prone, time‑consuming, and inconsistent.
We need the system to automatically allocate (amortize) the spending to monthly periods, driven by the service period captured at PR/PO, without any manual AP intervention.

Business Background

Example: Annual SaaS subscriptions, support contracts, or licenses.