salt the books
1. To falsify the information in a financial transaction, invoice, or account to make it seem more valuable. The tax auditors were shut down and the top bosses sent to jail for salting the books of dozens of clients' accounts.
2. To plant false information about something to fraudulently increase its value, potency, or desirability. After the dossier circulated the media, nearly culminating in the president's impeachment, it came to light that the senator's campaign had heavily "salted the books" with falsified accounts of witnesses who'd been paid to cooperate.