The Short Answer: Delta 30 Earns More, Delta 20 Protects More

If you sell a covered call at a delta of 0.30, you collect roughly 50% more premium than a delta 0.20 call on the same stock and expiration — but you also face a higher chance your shares get called away. Delta 20 strikes sit farther out of the money, so you keep more upside and face less assignment risk, at the cost of thinner premium. Most retail covered-call sellers land somewhere between these two numbers, and choosing correctly depends on three things: how badly you want to keep the stock, how much income you need, and what implied volatility is doing right now.

This article walks through both strikes with real numbers, explains the probability math behind each, and helps you decide which fits your situation.

What Delta Actually Tells a Covered-Call Seller

Delta measures how much an option's price moves for every $1 move in the underlying stock. A call with a delta of 0.30 gains roughly $0.30 in value when the stock rises $1. But for covered-call sellers, delta carries a second, more useful meaning: it approximates the probability that the option expires in the money.

A delta 0.30 call has roughly a 30% chance of expiring in the money — meaning there is about a 30% chance your shares get called away at expiration. A delta 0.20 call carries roughly a 20% chance of assignment. Flip those numbers and you get the probability of expiring worthless: about 70% for the delta 30 call and 80% for the delta 20 call. The Options Industry Council (OIC) describes this probability interpretation as a practical rule of thumb, not a guarantee, because delta shifts constantly as price and volatility change.

For covered-call sellers, a higher delta means more premium collected and more assignment risk. A lower delta means less premium and more breathing room.

Worked Example: AAPL Covered Call, Delta 30 vs Delta 20

Let's use Apple (AAPL) trading at $213 per share as of a recent session. You own 100 shares and want to sell a 30-day call.

**Delta 0.30 strike — the $220 call:** The $220 call (roughly $7 out of the money) carries a delta near 0.30. It might be quoted at $3.10 bid / $3.20 ask. Selling at the midpoint of $3.15 puts $315 in your pocket per contract. That is a 1.48% return on your $213 stock cost in 30 days, or roughly 17.8% annualized if you repeat it every month. Your stock gets called away if AAPL closes above $220 at expiration. Your effective sale price would be $220 + $3.15 premium = $223.15, which is still a gain from $213.

**Delta 0.20 strike — the $225 call:** The $225 call (roughly $12 out of the money) carries a delta near 0.20. It might be quoted at $1.55 bid / $1.65 ask. Selling at the midpoint of $1.60 puts $160 in your pocket per contract. That is a 0.75% return in 30 days, or about 9% annualized. Your stock gets called away only if AAPL closes above $225 at expiration. You keep all gains up to $225, and your effective sale price if assigned is $225 + $1.60 = $226.60.

**The trade-off in plain numbers:** - Delta 30 earns $155 more per contract over 30 days. - Delta 20 lets AAPL run $5 higher before you lose shares. - Delta 30 has roughly a 30% assignment probability; delta 20 has roughly 20%.

Over 12 months, if you sell delta 30 calls every month and collect $315 each time, you generate $3,780 per 100 shares — assuming no assignment. The delta 20 path generates $1,920 per 100 shares on the same assumption. The gap is real, but so is the difference in risk.

Risks You Need to Understand Before Picking a Strike

Covered calls cap your upside. That is not a footnote — it is the central trade-off. If AAPL jumps from $213 to $240 in a single month, the delta 30 seller at the $220 strike misses $17 of that gain per share (minus the $3.15 premium kept). The delta 20 seller at $225 misses $12 of that gain (minus the $1.60 premium). Neither seller participates fully in a strong rally.

**Assignment risk is real and can happen early.** American-style equity options — which cover most US-listed stocks — can be exercised at any time before expiration, not just at expiration. FINRA and the OIC both note that early assignment most often happens when a call goes deep in the money or just before an ex-dividend date. If you sell a delta 30 call and the stock surges, your delta can quickly move toward 0.50 or higher, and early assignment becomes a genuine possibility.

**Volatility crush can hurt you in unexpected ways.** If implied volatility drops sharply after you sell, the option loses value faster than expected — which is good if you want to buy it back cheaply. But if you were counting on high premium repeating next month, lower IV means thinner premiums ahead.

**Tax treatment matters.** In the US, the IRS classifies most covered-call premiums as short-term capital gains, regardless of how long you have held the stock. Selling calls that are too deep in the money can also disqualify your holding period for long-term capital gains treatment on the stock itself — a rule covered in IRS Publication 550. Canadian investors should note that the CRA treats option premiums as capital gains or income depending on your trading frequency and intent. Consult a tax professional before building a high-volume covered-call strategy.

When Delta 30 Makes More Sense

Choose a delta 30 strike when:

**You are neutral to mildly bearish on the stock.** If you think AAPL is likely to trade sideways or drift lower, the extra premium from the delta 30 call cushions a flat or declining stock price better than the thinner delta 20 premium.

**Implied volatility is low.** When IV is compressed, premiums across all strikes shrink. Selling a delta 20 call during a low-IV environment might generate only $0.80 or $0.90 per contract — barely worth the trade. Moving out to delta 30 at least keeps the income meaningful.

**You are willing to sell the stock at the strike.** If you bought AAPL at $170 and it is now at $213, selling the $220 call and getting called away at $223.15 is still a strong outcome. Delta 30 works well when you have a large unrealized gain and would not mind locking it in.

**You are running a monthly income strategy.** Traders who treat covered calls as a primary income source often target delta 25-35 because the premium-to-risk ratio is more efficient for generating consistent monthly cash flow.

When Delta 20 Makes More Sense

Choose a delta 20 strike when:

**You want to keep the stock long-term.** If AAPL is a core holding you plan to own for years, giving it room to run matters more than squeezing out extra premium. Delta 20 lets the stock climb $12 before you face assignment, versus only $7 with delta 30.

**Implied volatility is elevated.** When IV spikes — around earnings, macro events, or broad market selloffs — even delta 20 calls pay attractive premiums. You get the safety of a farther strike without sacrificing much income.

**You are approaching an earnings date.** Selling a delta 30 call into earnings is aggressive. A surprise beat can send the stock well past your strike overnight. Delta 20 gives you a wider buffer, though many experienced sellers skip the earnings week entirely or use a much shorter expiration.

**You have a specific price target.** If you believe AAPL is fairly valued at $225 and would sell there anyway, the delta 20 call at $225 aligns your covered-call strategy with your investment thesis.

How to Combine Both Approaches Over Time

You do not have to pick one delta and stick with it forever. Many retail covered-call sellers adjust their strike selection based on market conditions each month.

A practical framework: check the CBOE Volatility Index (VIX) before selecting your strike. When VIX is below 15, IV is generally low across the market. Lean toward delta 30 to maintain income. When VIX is above 20, IV is elevated and even delta 20 strikes pay well — use the wider strike to protect your position.

You can also split a larger position. If you own 200 shares of MSFT, sell one contract at the delta 30 strike and one at the delta 20 strike. You collect blended premium and split your assignment exposure. This is not a complex strategy — it is just averaging your strike selection across two contracts.

Track your results over at least six months before drawing conclusions. The CBOE has published research showing that systematic covered-call strategies — like those tracked by the CBOE S&P 500 BuyWrite Index (BXM) — tend to outperform buy-and-hold in flat and declining markets but lag in strong bull runs. That pattern holds whether you sell delta 30 or delta 20 calls. The difference between the two strikes is a matter of degree, not a fundamental change in strategy.

Is delta 30 or delta 20 better for covered calls?

Neither is universally better — it depends on your goal. Delta 30 generates roughly 50% more premium but carries a higher chance your shares get called away. Delta 20 pays less but gives your stock more room to rise before assignment. Match the strike to whether you prioritize income or keeping the stock.

What is the probability of assignment at delta 30 vs delta 20?

Delta approximates the probability that an option expires in the money. A delta 0.30 call has roughly a 30% chance of expiring in the money, meaning about a 30% assignment probability at expiration. A delta 0.20 call carries roughly a 20% chance. The Options Industry Council (OIC) notes this is a useful estimate, not a precise guarantee, since delta changes as the stock moves.

How much more premium does a delta 30 call pay compared to delta 20?

The difference varies by stock and implied volatility, but on a stock like AAPL trading near $213, a delta 30 call might pay around $3.15 per share while a delta 20 call pays around $1.60 — roughly double the premium. In dollar terms that is about $155 more per contract per month, though the gap narrows when implied volatility is high.

Can I get assigned early on a covered call?

Yes. US-listed equity options are American-style, meaning the buyer can exercise at any time before expiration. Early assignment most often happens when a call moves deep in the money or just before an ex-dividend date, as noted by FINRA and the OIC. Selling delta 30 calls increases the chance your option moves deep in the money quickly, raising early-assignment risk compared to delta 20.

How does implied volatility affect which delta I should choose?

When implied volatility is low, premiums shrink across all strikes, making delta 20 calls pay very little. In low-IV environments, moving to delta 30 helps maintain meaningful income. When IV is elevated — often tracked through the CBOE VIX — even delta 20 calls pay attractive premiums, so you can afford the wider, safer strike without sacrificing much income.

Does selling covered calls affect my taxes on the stock?

In the US, covered-call premiums are generally treated as short-term capital gains by the IRS, and selling calls that are too deep in the money can disqualify the holding period needed for long-term capital gains treatment on the stock, as detailed in IRS Publication 550. Canadian investors should check with a tax professional, since the CRA's treatment of option premiums depends on trading frequency and intent. Always consult a qualified tax advisor before running a systematic covered-call program.