By default in the DealPOS application, the Invoice number template for sales, purchases, adjustments, etc. transactions has the same format. If you want to differentiate the invoice number template for each transaction, you can add a differentiator at the beginning of the invoice number. For detailed configuration steps, you can check the explanation below:
I. Configuration through Setup Menu
Step 1. Select application configuration in Setup Menu

Step 2. Select Transaction Numbering section then change the Prefix

II. Result
Sell:

Buy:

Estimate:

Adjustment:

Adding Prefix for Transaction Number Tutorial Video
You might also like to read this article:
To change the invoice format, you can check the following article: Invoice Numbering Options Format
Do you have multiple outlets? You can differentiate the Invoice code for each outlet. For more information, see this article: Assign Prefix Invoice Number by Outlet Code