There are four methods to override the pricing in a bill manually. For this article, we will assume you want the price to go down. Each method is below.
Method 1
Add an item in the negative to reduce the "Total Charges" on the bill.
Most common scenario: Guest needs a lodging discount
Step 1.) Click ADD button under the booking information.
Step 2.) In the popup modal, select the Lodging Discount item from your list of items. Enter the amount in the negative that you wish to discount. Do this with a hyphen or dash to indicate that you wish to reduce the total charges on the bill.
Step 3.) Click the Add button.
Setup: Ensure that you have a "Lodging Discount" or similar Item setup in Settings → Items
In Settings → Items, you will be able to click the New button and create an item such as "Room Discount," "Lodging Discount," or "Adjustment." Make sure to apply the same taxes to this item as you have applied to the room charges that you wish to discount. You can also attribute them to the same Revenue Account as your room revenue if you wish. You can track these discounts in your Revenue by Item report.
Method 2
Edit the price of one or more line items, including the room rate, to a lower price.
Step 1.) Hover your mouse over the item or "Room." Click to highlight it in blue. Then click the edit button. 
Step 2.) In the Edit Item popup modal, edit the price of the room and click Update.
Note that if you adjust the room rate, it will affect your ADR.
Method 3
Switch the room reservation into a rate type where the price is less.
Step 1.) Click the Edit button on the right of the booking. 
Step 2.) In the Edit Booking modal, click the drop-down box under Rate and select a different rate type, such as your generic 15% discounted rate type, military rate, etc. Click Update.
Setup: Ensure that you have created a rate type with discounted pricing first. You can track these with your Revenue by Rate Type report.
► Related: Managing and creating Rate Types
This is the least common as it does not affect the Total Charges, but it still provides you with a traceable way to reduce the Remaining Balance.
► Related: Managing and creating Rate Types
Method 4
Add a payment onto the bill on behalf of the customer.
This is the least common as it does not affect the Total Charges, but it still provides you with a traceable way to reduce the Remaining Balance.
Step 1.) In the Payments section, click the green payment icon.
Step 2.) In the Payment popup modal, select a Comp or similar custom payment type from the Payment Type drop down box.
Step 3.) Enter an optional note in the Reference Number field.
Step 3.) Click the Take Payment button to the right of the amount field to post the payment.
Setup: Ensure that you have a custom payment type to make these adjustments first.
Settings → Payment Types. You will be able to create a new custom payment type such as "Comp" or "Admin Adjustment" or similar. You can track these in the Payments by Type report.
Settings → Payment Types. You will be able to create a new custom payment type such as "Comp" or "Admin Adjustment" or similar. You can track these in the Payments by Type report.