Approving costs is one route; approving the budget itself is another.
Approval signers
A budget can have Approval Signers: the people inside your company who must approve the budget before it can be published. Add them on the budget. Each signer approves in Tubes; the budget shows who has approved and who is still awaiting.
An administrator can define default signers per project so that new budgets on a project already carry the right people.
Status
When the signers have approved, the budget gets the status Approved (or the name your account uses). If the work budget feature is on, approving the budget can create the work budget in the same step; removing the approval removes the work budget again, so decide before production starts working in it.
Client approval
The client does not approve inside Tubes. They receive a quotation, approve it by signing (DocuSign or DocuSeal) or by replying, and you set the quotation and budget status accordingly. See Create a quotation.
Publication
Approval and publication are separate steps. A budget that is approved but not published is not yet available to the production team. See Publish a budget and create a work budget.