Money and currencies

Thresholds are the heart of transaction monitoring — “more than GHS 50,000”, “just under the reporting limit”. For a threshold to mean anything, every amount has to be stored exactly and compared in the same currency. This page explains how SpeculaPro does that, and what you need to send it.

Three rules for money

1. Amounts are whole numbers of the smallest unit. No decimals, ever.
2. Every amount is also converted into your base currency, and the rate used is stored.
3. Thresholds are compared in the base currency, so one rule works across every currency your customers use.

Minor units

Every amount is stored as an integer count of the currency’s minor unit — pesewas for the cedi, cents for the dollar.

Amount	Currency	Stored as
GHS 12.50	GHS	1250
GHS 50,000.00	GHS	5000000
USD 300.00	USD	30000
XOF 25,000	XOF (no minor unit)	25000

Why not decimals?

Decimal and floating-point arithmetic in computers can produce tiny rounding errors — 0.1 plus 0.2 is not exactly 0.3. In a system that adds up thousands of payments to compare against a threshold, those errors can tip a total over or under the line. Whole numbers never round.

Send minor units, not decimals

When your systems send a transaction, the amount must be in minor units with its currency code. Sending 12.50 where 1250 is expected — or the other way round — is the most common integration mistake, and it makes every threshold off by a factor of 100. Check a few transactions end to end when you first connect.

Base currency and conversion

Each workspace has a base currency — GHS for a Ghanaian institution. Every transaction is stored with:

Field	Meaning	Example
Amount (minor units)	In the transaction’s own currency	30000
Currency	ISO code	USD
Amount in base (minor units)	Converted into the base currency	465000
Base currency	The workspace’s	GHS
FX rate	The rate used	15.5

In that example, USD 300.00 at 15.5 cedis to the dollar is stored as GHS 4,650.00.

The FX rate table

Each workspace keeps a table of daily exchange rates: for each date, how many units of the base currency one unit of another currency is worth, and where the rate came from — for example the Bank of Ghana’s published rate.

Rates are kept forever. That is what makes every conversion reproducible: years later you can show exactly which rate turned a USD transfer into the cedi figure a rule compared against its threshold.

Why store the rate on every transaction?

Exchange rates move daily. If conversions were done at the time a report is run, the same transaction could cross a threshold one month and not the next. Storing the converted amount and the rate at the time of the transaction means the figure a rule saw never changes.

Worked example: a threshold across currencies

Rule A3 Large cross-border transfer has threshold_amount set to GHS 50,000. Three transfers arrive the same day; the rate is 15.5 GHS/USD and 16.8 GHS/EUR.

Transfer	Original	In base	Hits?
1	USD 3,000	GHS 46,500	No
2	EUR 3,200	GHS 53,760	Yes
3	GHS 52,000	GHS 52,000	Yes

One threshold, set once in cedis, applies correctly to all three.

Calendar days and timezones

Rules that say “per day” or “per month” — daily KYC tier limits, for example — count days in the workspace timezone (Africa/Accra by default). A transaction at 23:30 in Accra counts towards that day, even if a server elsewhere would call it the next day.

Related

• Workspaces and tenancy
• A. Thresholds and reporting
• Data model