What is cost basis, and how do options lower it?
In one line: Cost basis is what you paid for your shares, per share; option sellers often track it net of the premiums they've collected, which lowers the price the stock must hold to break even.
How it works
Cost basis is what you paid for your shares. Buy 100 shares at $50 and your cost basis is $50 a share, or $5,000.
Option sellers track a second number: the cost basis after premiums. Each premium you collect on those shares lowers it a little. Sell a call for $1.00 on $50 shares, and your net cost is $49.
In the wheel strategy, this number starts before you own anything. You sell a Cash-secured put. If you're assigned, the put's premium lowers what you really paid. Then each Covered call lowers it again.
An example (hypothetical)
XYZ trades at $50 (an illustration, not a trade idea). Here's one wheel cycle that goes wrong, tracked per share.
| Step | Cash in or out | Your net cost per share |
|---|---|---|
| Sell a $45 put for $1.00 | +$100 | — |
| Assigned: buy 100 at $45 | −$4,500 | $45 − $1.00 = $44.00 |
| Sell a $47 call for $0.80. It expires | +$80 | $44 − $0.80 = $43.20 |
| XYZ slides. You sell the shares at $40 | +$4,000 | Result: ($40 − $43.20) × 100 = −$320 |
The premiums helped. Without them, selling at $40 would have been −$500. With them, it's −$320. But it's still a loss. Lowering your basis doesn't stop the stock from falling below it.
Why it matters for sellers
Your net cost basis is your real break-even on the shares. Know it before every call you sell. A call with a strike below it can lock in a loss if the shares are called away. Our cost basis after assignment page shows that trap step by step.
Keep two records. The tracking basis above is for your decisions. Your tax basis follows tax rules. In the US, an assigned put's premium usually lowers the tax basis of the shares. A covered call's premium is usually handled separately, or added to the sale price if the shares are called away. This is general information, not tax advice. Check with a tax professional or your broker.
In Canada, gains inside a TFSA or RRSP aren't taxed as they happen, but tracking basis still matters for your decisions. Covered calls are widely allowed in those accounts; cash-secured puts depend on the broker, and options permissions differ by broker.
Questions
Does selling covered calls lower my cost basis?
In your own tracking, yes: each premium lowers what you've really paid per share. For taxes, the rules are different. Check how your broker reports it.
Can my cost basis go to zero?
In tracking, with enough premiums over a long time, it can fall a lot. But the shares can fall faster. A low basis is a record, not protection.
Should I ever sell a call below my cost basis?
Only if you'd truly accept selling at a loss. If the stock jumps and the shares are called away, the loss becomes real.
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