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SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS AND RESERVES | 12 Months Ended
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Sep. 30, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] |
SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS AND RESERVES | TETRA TECH, INC. SCHEDULE II – VALUATION AND QUALIFYING ACCOUNTS AND RESERVES For the Fiscal Years Ended October 2, 2016, October 1, 2017 and September 30, 2018 (in thousands)
|  | Balance at Beginning of Period |  | Charged to Costs, Expenses and Revenue |  | Deductions (1) |  | Other (2) |  | Balance at End of Period
Allowance for doubtful accounts: |  |  |  |  |  |  |  |  |  |
Fiscal 2016 |  | $ | 31,490 |  |  | $ | 8,082 |  |  | $ | (12,191 | ) |  | 7,852 |  |  | $ | 35,233 |
Fiscal 2017 |  | 35,233 |  |  | 2,848 |  |  | (6,233 | ) |  | 411 |  |  | 32,259 |
Fiscal 2018 |  | 32,259 |  |  | 7,167 |  |  | (4,485 | ) |  | 2,639 |  |  | 37,580 |
Income tax valuation allowance: |  |  |  |  |  |
Fiscal 2016 |  | $ | 7,791 |  |  | $ | 3,856 |  |  | $ | — |  |  | $ | 13,800 |  |  | $ | 25,447 |
Fiscal 2017 |  | 25,447 |  |  | (121 | ) |  | — |  |  | — |  |  | 25,326 |
Fiscal 2018 |  | 25,326 |  |  | 900 |  |  |  |  | (4,747 | ) |  | 21,479 |
(1) | Primarily represents uncollectible accounts written off, net of recoveries.
(2) | Includes allowances from new business acquisitions, loss in foreign jurisdictions, currency adjustments, and valuation allowance adjustments related to net operating loss carry-forwards.

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- Definition The entire disclosure for valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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- References No definition available. + Details
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