# Map currencies and timezones before merging anything

> Tier: recipe. Operating recipe: real tool sequence, core rules, known traps.

The pre-merge map: which account reports in what currency and timezone, and the rule chosen for the merge.

**Intent.** The conversion and alignment rules every merged table needs.

## When to use

- Before any multi-account or multi-platform table.
- Onboarding.

## When not to use

- No specific contraindication beyond the preconditions below.

## Sources

Required: any connected source

## Preconditions

- The account is ticked in the dashboard, confirmed via list_accounts.

## Inputs

- `window`: Analysis window. Default: last 30 days.

## Procedure

1. Read currency and timezone per account. — tools: `google_ads_get_account_details`, `tiktok_get_advertiser_info`, `ga4_get_property_configuration`
2. Write the merge rule: target currency, conversion basis, day boundary.

## Decision rules

- **When** Accounts mix currencies → **conclude** Pick and state one target and one conversion basis: a merged table without the rule is unauditable.

## Evidence requirements

- Every figure carries its account, metric and window.
- Anything below a readable sample size is reported as unjudged, not as zero.

## Human approval boundary

- The readout changes nothing. Any change it motivates goes through Safe Writes: preview, human confirmation, then apply.

## Failure modes

- Converting a month at today's rate distorts dailies: period-average or per-day rates, stated.

## Output

- **Readout**: The figures, with windows and accounts named.
- **Flags**: What deserves a deeper skill or a human decision.