The Scots writer boosted the coffers of his company as royalties rolled in from the comeback of the hard-bitten Edinburgh detective.
New figures from his firm John Rebus Limited, named in honour of his famous creation, show it has total assets of £2,054,508.
The accounts, which have just been filed at Companies House, reveal Rankin, 53, owes £518,824 to unnamed creditors. That leaves the firm's value at £1,536,920 - up more than £1m from the previous year's figure of £521,921.
Rankin, who has sold more than 20 million books, is currently taking a year off writing after a busy spell which saw him bring back Detective Inspector Rebus following a five-year absence. The no-nonsense detective teamed up with new character Malcolm Fox in the novels Standing In Another Man's Grave and Saints Of The Shadow Bible.
Rankin, of Edinburgh, set up John Rebus Limited in 2001 to channel his earnings from his books. The decision followed an investigation by the taxman into unfounded claims he was not declaring enough income when filling out tax returns himself.
He set up the company after he was forced to spend months searching for old paperwork to convince inspectors he was not lying about his earnings. Fife-born Rankin is a director of the company along with his wife Miranda Harvey.