Unexpected results from MSQuery

I am not certain what the criteria should be but I think probably:

SELECT SALES_LEDGER.ACCOUNT_NAME, SALES_LEDGER.VAT_CODE, SALES_TRANSACTIONS.TRANSACTION_TYPE, SALES_TRANSACTIONS.GOODS_AMOUNT, SALES_TRANSACTIONS.TRANSACTION_DATE
FROM ACCOUNTING_SYSTEM.SALES_LEDGER SALES_LEDGER, ACCOUNTING_SYSTEM.SALES_TRANSACTIONS SALES_TRANSACTIONS
WHERE SALES_LEDGER.THIS_RECORD = SALES_TRANSACTIONS.PARENT_RECORD AND ((SALES_TRANSACTIONS.TRANSACTION_TYPE=5) OR (SALES_TRANSACTIONS.TRANSACTION_TYPE=4)) AND SALES_LEDGER.VAT_CODE=4

You should probably be posting your question here.

Anyway, let's look at your problem from a logical standpoint.

Your WHERE clause

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What I usually do is, I split "AND" conditions by row, and "OR" conditions in the same row. So it would look like this for you

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When split like this, it is visually easy to spot what went wrong.

I assume you want it to be a TRANSACTION_TYPE of "4" or "5" and it must have VAT_CODE of "4"?
So it should look like this:

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And when you want to combine it back to a single line, always bracket "OR" conditions (as shown above).

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