What is the entry for discount allowed

Is the discount allowed to be in the profit and loss statement?

It depends on when the sales discount is taken.

For example if a customer purchases something on credit, then pays within the discount period the journal entry will be:
Debit cash for the amount of cash
Debit Sales discount for the difference
Credit Accounts Receivable for the amount the customer owes

For an example if a customer purchases $100 of goods on credit and there is a discount of $10 if the bill is paid within 15 days, the journal entry will be:
Debit Cash for $90
Debit Sales Discount for $10
Credit Accounts Receivable for $100

On a Multi-Step Income statement Sales discount will be listed after gross sales.

First will be Gross Sales, then Sales discounts and Sales Returns & Allowances will be listed, which will reduce gross sales to get to Net Sales.

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