If you don't want to hold your TIPS to maturity, you have to sell it on the secondary market.

Selling is the opposite of buying. A good time to buy TIPS is usually a bad time to sell. Between two TIPS bonds, if one issue looks like a better deal to buy, it's usually also a bad choice to sell.

When you buy TIPS on the secondary market, you pay a markup above the wholesale price. When you sell TIPS on the secondary market, you pay a markdown below the wholesale price and you receive less.

Because of these markups and markdowns, I can only think of two limited cases when it makes sense to sell TIPS on the secondary market:

• Long term TIPS yields are high and you'd like to extend your inflation protection by selling short-term TIPS and buying long-term TIPS. You lock in the good yields for more years.
• Long term TIPS yields are low and you'd like to lock in some gains and wait for better opportunities in the future. Please note the better opportunities may not come any time soon.

In most cases you should hold your TIPS to maturity.

If you hold your TIPS at TreasuryDirect (taxable accounts only), TreasuryDirect offers a service called SellDirect. They ask for quotes from three dealers. They pick the highest bid and then charge you $45 commission. They won't tell you what the price is before you agree to the sale. You will get whatever price they get minus the $45 fee.

If you hold your TIPS at a brokerage firm, you will have to ask the bond desk at the broker what the bid price is. Some brokers have an online interface for selling. Some don't and you have to call.

Just like buying TIPS on the secondary market, it's probably a good idea to call instead of taking the price quoted online. The broker on the other side of the line may get you a better price, more than compensating the higher commission.