> For the complete documentation index, see [llms.txt](https://docs.filed.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.filed.com/reference/products/ai-review/prior-year-comparison.md). # Prior-year comparison ## The prior year as a baseline Filed uses the client's prior-year return as a baseline in two related places: during AI Tax Prep's reconciliation step, and on AI Review's leadsheets. Both draw from the same underlying idea - a current-year value is easier to judge with the prior year sitting right next to it - but they serve different moments in the workflow. ## During AI Tax Prep: reconciliation When a prior-year tax-software backup is available, AI Tax Prep's reconciliation phase compares newly extracted data against it to resolve sources of truth and flag conflicts it can't resolve automatically. This is what powers the missing-documents checklist (a document type present last year but absent this year gets flagged - see [Missing documents](/reference/products/binder/missing-documents-tracking.md)) and feeds some of the Observations severity flags described in [Pre-Entry Notes Notifications](/reference/products/ai-tax-prep/pre-entry-notes-notifications.md). See [How Filed processes the documents](/reference/products/ai-tax-prep/workflow-overview.md#how-filed-processes-the-documents). ## On leadsheets: the prior-year value alongside the current one Once a return reaches AI Review, leadsheet rows can show the prior-year value directly alongside the current figure, so a meaningful year-over-year change (a dividend total that doubled, a deduction that disappeared entirely) is visible without pulling up last year's return separately. When a current-year figure is itself a rollup of several source documents, the row also shows the individual components that were summed to reach it - so an unexpected prior-year jump can be traced down to which specific component changed. See [Tracing a figure back to its source and prior year](/reference/products/binder/leadsheets.md#tracing-a-figure-back-to-its-source-and-prior-year). ## Why this catches things a straight document-to-return check would miss A discrepancy check that only looks at the current year's documents can miss things that are only obvious in context - an amount that's correct on its own but wildly different from every prior year, for instance. Comparing against the prior year surfaces exactly this kind of change for a human to judge, without requiring the reviewer to remember or look up what last year's return said. ## Where to look * Before data entry, in AI Tax Prep: [Pre-Entry Notes](/reference/products/ai-tax-prep/pre-entry-notes-tab.md) and the missing-documents checklist. * During review, in AI Review: leadsheet rows in the [Leads tab](/reference/products/binder/leadsheets.md#tracing-a-figure-back-to-its-source-and-prior-year). --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.filed.com/reference/products/ai-review/prior-year-comparison.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.