Perps
Carry
Comet perps have no funding payments between longs and shorts. A position pays the borrow rate on what it owes and earns the supply rate on what it holds; the difference is its carry.
The formula
Both rates are the reserve rates of the two tokens in the position. A long on SOL-PERP pays USDC’s borrow rate and earns SOL’s supply rate; a short pays SOL’s borrow rate and earns USDC’s supply rate.
Worked example
Take 1,000 USDC of margin at 5× with SOL at 200, and suppose the USDC reserve is 72% utilized and the SOL reserve 60%.
| Owes | Pays | Holds | Earns | Carry per year | |
|---|---|---|---|---|---|
| Long | 4,000 USDC | 5.08% = 203 | 25 SOL | 2.04% = 102 | 101 USDC |
| Short | 25 SOL | 4.00% = 200 | 6,000 USDC | 3.29% = 198 | 2 USDC |
On a 5,000 USDC position that is 2.03% a year for the long and 0.05% for the short.
How carry balances longs and shorts
Carry does the work that funding does on an order-book perp, through the reserves. When longs outnumber shorts:
- Longs borrow USDC, so USDC utilization and its borrow rate rise. Longs pay more.
- Longs supply the SOL they hold, so SOL utilization and its borrow rate fall. Shorts pay less.
The reverse holds when shorts lead. What either side pays goes to the reserve’s suppliers.
Accrual
Carry accrues continuously through the reserves’ indexes. There are no settlement times: a position’s equity reflects its carry in every slot, and closing settles it in full.