Under ASC 606 Contract Modifications, a change in the scope or price of a contract is accounted for as either a new separate contract or a modification of the existing contract, depending on whether the change adds distinct goods or services at their standalone selling price.
ASC 606-10-25-10 defines a contract modification as a change in the scope or price (or both) of a contract that is approved by the parties. Approval can be written, oral, or implied by customary business practice — but unapproved changes create a variable consideration question, not a modification.