Write an article based on this summary:

Compare prices. Make sure your offset will be retired. Complete your transaction. Purchase additional carbon offsets when traveling by air. Advertise your business’s carbon neutrality.
The cost for carbon offsets varies greatly depending on the expense of the project as well as the general laws of supply and demand. You can expect to pay anywhere from $10 to $50 per metric ton of carbon dioxide emissions. Keep in mind that just because one offset is more expensive than another, that doesn't necessarily mean it's better quality. Do your research on the projects independently of price, then choose a high-quality offset that best fits your budget. You can't claim the benefit of your carbon offset until it is retired. Once the offset is retired, it cannot be resold to anyone else. Retirement indicates that the specific amount of carbon dioxide you purchased has in fact been reduced or eliminated. For smaller-scale transactions, you typically don't have to worry about retirement – retailers automatically retire the carbon offsets when they're purchased. However, in the case of a larger purchase of carbon offsets, it may take some time before retirement can take place. Once you've decided which carbon offset project you want to support, you typically can purchase your offset online using your credit card. Determine how many offsets you want to purchase and make sure the provider has that many available. Make sure you get a receipt for your purchase. In some countries, carbon offsets may be tax deductible. Airplanes contribute considerable global carbon emissions. Many airlines as well as travel agencies provide the opportunity for you to purchase an offset when you book a flight.  These offsets are calculated for you personally based on the environmental impact of the flight you're taking. If you purchase an offset through the airline, typically the cost for the offset is simply added to the price for your ticket. Particularly if you're buying carbon offsets for a small business, your customers will want to know that your business is socially and environmentally responsible. Avoid advertising carbon neutrality until your carbon offsets have been retired. You also might consider having your carbon neutrality certified by a third-party organization.