Deposit Amount not getting applied fully against Transaction (Excluding VAT Amount)

Hi Experts

Deposit Amount is not getting applied against Transaction Full Amount.

Its getting applied but excluding Tax Amount.

Scenario:-

1. Create a Deposit Transaction 2000

2. Create Invoice with amount 1000 (+ Vat 50)= 1050

3. while creating Invoice, I enter Deposit number in Commitment Column

4. Once the Transaction is saved, Deposit amount is getting applied Transaction Amount 1000 but excluding VAT 50

Please advise