Automation library · Money admin

Detect duplicate invoices with Google Sheets and Gemini

Started by a change in a Google Sheet, and works across Google Sheets and Slack. It hands the judgement calls to Gemini. 17 steps, 1 branch: a working afternoon to understand properly.

MediumCalls a model: Gemini

Download free
17 stepsMedium: a working afternoon
1Branch: places the flow splits
0Loops or waits
2Services it connects to

The flow

Starts it 1Model 2Logic 9Service 5

The steps in the order they run, from what starts it.

  1. 1Google Gemini Chat ModelLm Chat Google GeminiModel
  2. 2New Invoice Submission TriggerGoogle Sheets triggerStarts it
  3. 3AI Duplicate Risk AssessmentChain LlmModel
  4. 4Retrieve Invoice HistoryGoogle SheetsService
  5. 5Prepare Incoming InvoicesAggregateLogic
  6. 6Extract AI Investigation ResultsCodeLogic
  7. 7Prepare Historical RecordsAggregateLogic
  8. 8Consolidate Invoice DataMergeLogic
  9. 9Combine Detection & AI ResultsMergeLogic
  10. 10Duplicate Detection EngineCodeLogic
  11. 11Prepare Investigation RecordSetLogic
  12. 12Fraud Risk Decision GatewayIfLogic
  13. 13Notify Accounts Payable TeamSlackService
  14. 14ERP Payment Hold RequestHttp RequestService
  15. 15Combine Investigation OutcomeMergeLogic
  16. 16Record Approved InvoiceGoogle SheetsService
  17. 17Record Fraud Investigation CaseGoogle SheetsService

How it's built

Starts on
A change in a Google Sheet
Steps
17, with 1 branch
Size
Medium: a working afternoon
Connects to
Google Sheets, Slack
Model
Gemini

Questions

What does it need to run?

An n8n account, plus your own Google Sheets and Slack accounts, and a key for Gemini. You connect your own accounts after importing it; none are included.

What starts it?

It starts on a change in a Google Sheet.

Does it use AI?

Yes. It calls Gemini. Model calls are billed by the provider, not by n8n.

How long does it take to set up?

Plan an afternoon. 17 steps is enough that you should read each one before running it.

How do I import it?

Copy the workflow, open a new workflow in n8n and paste. The steps appear on the canvas, ready for your own accounts.

Before you run it

Nothing here has been tested by us. It is somebody's working automation, read and described from its own steps. Treat the connections it wants as a list of accounts it will touch, and read the 17 steps before you point it at anything that matters.