Added description of each entry in red to explain entry.
Item 1 is recording Expense/Assets for AMEX purchases.
Item 2 is recording Cash entries between A, B and AMEX.
Company A:
1a) Debits Expense or Asset for AMEX purchases $700*
Credits CC liability account for AMEX purchases $700
To record Expense or Asset bought on Co A's AMEX
1b) Debits current asset: "Amount Due from Co B" $300
Credits CC liability account for AMEX purchases $300
To record Co B purchase on Co A's AMEX to be re-paid
2a) Debits CC liability account for AMEX purchases $1000
Credits Current asset "Amount Due from Co B" $300
Credits Cash/Bank account for AMEX payment $700
To record payment to AMEX and payment from Co B
Company B:
1c) Debits Expense or Assets for AMEX purchases $300*
Credits Current liability "Amount Due TO Co A" $300
To record Expense or Asset bought on Co A's AMEX
2b) Debits Current liability "Amount Due TO Co A" $300
Credits Cash/Bank for amount paid to A’s AMEX $300
To record payment to AMEX as repayment to Co A
