bracket creep

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A shift of personal income into a tax bracket with a higher tax rate as a result of inflation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun taxation Increased taxation that arises when an inflation adjustment to a wage or salary pushes a taxpayer into a higher tax bracket (or, in a progressive taxation regime, further into a bracket).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a movement into a higher tax bracket as taxable income increases