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Schedule I - Statements of Cash Flows (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2020 | Oct. 31, 2020 | Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Operating activities |  |  |  |  |  |  |  |  |  |  |  |  |
Net income attributed to common shareholders |  |  | $ 239.0 | $ 266.8 | $ 241.6 | $ 452.5 | $ 243.9 | $ 234.3 | $ 235.7 | $ 420.1 | $ 1,199.9 | $ 1,134.0 | $ 1,059.3
Reconciliation to cash provided by operating activities |  |  |  |  |  |  |  |  |  |  |  |  |
Equity income in subsidiaries, net of distributions |  |  |  |  |  |  |  |  |  |  | (29.1) | (2.9) | (18.6)
Deferred income taxes |  |  |  |  |  |  |  |  |  |  | 182.2 | 167.7 | 300.1
Loss on debt extinguishment | $ 10.5 | $ 27.9 |  |  |  |  |  |  |  |  | 38.4 | 0.0 | 0.0
Change in - |  |  |  |  |  |  |  |  |  |  |  |  |
Other current liabilities |  |  |  |  |  |  |  |  |  |  | (41.2) | 78.7 | (67.6)
Other, net |  |  |  |  |  |  |  |  |  |  | 3.4 | 20.6 | 290.4
Net cash provided by operating activities |  |  |  |  |  |  |  |  |  |  | 2,196.0 | 2,345.5 | 2,445.5
Investing activities |  |  |  |  |  |  |  |  |  |  |  |  |
Capital contributions to subsidiaries |  |  |  |  |  |  |  |  |  |  | (21.2) | (52.6) | (53.5)
Other, net |  |  |  |  |  |  |  |  |  |  | (5.3) | 16.5 | 20.5
Net cash used in investing activities |  |  |  |  |  |  |  |  |  |  | (2,806.8) | (2,494.9) | (2,384.4)
Financing activities |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise of stock options |  |  |  |  |  |  |  |  |  |  | 43.8 | 67.0 | 29.1
Purchase of common stock |  |  |  |  |  |  |  |  |  |  | (99.2) | (140.1) | (72.4)
Dividends paid on common stock |  |  |  |  |  |  |  |  |  |  | (798.0) | (744.5) | (697.3)
Issuance of long-term debt |  |  |  |  |  |  |  |  |  |  | 2,373.6 | 1,895.0 | 1,740.0
Retirement of long-term debt |  |  |  |  |  |  |  |  |  |  | (1,767.0) | (360.1) | (953.3)
Issuance of short-term loan |  |  |  |  |  |  |  |  |  |  | 340.0 | 0.0 | 0.0
Payments for debt extinguishment and issuance costs |  |  |  |  |  |  |  |  |  |  | (55.8) | (12.5) | (9.5)
Other, net |  |  |  |  |  |  |  |  |  |  | (11.4) | (9.9) | (5.7)
Net cash used in financing activities |  |  |  |  |  |  |  |  |  |  | (601.1) | (85.6) | (26.4)
Cash and cash equivalents at beginning of year |  |  |  |  |  | 37.5 |  |  |  | 84.5 | 37.5 | 84.5 |
Cash and cash equivalents at end of year | 24.8 |  | 24.8 |  |  |  | 37.5 |  |  |  | 24.8 | 37.5 | 84.5
WEC Energy Group |  |  |  |  |  |  |  |  |  |  |  |  |
Operating activities |  |  |  |  |  |  |  |  |  |  |  |  |
Net income attributed to common shareholders |  |  |  |  |  |  |  |  |  |  | 1,199.9 | 1,134.0 | 1,059.3
Reconciliation to cash provided by operating activities |  |  |  |  |  |  |  |  |  |  |  |  |
Equity income in subsidiaries, net of distributions |  |  |  |  |  |  |  |  |  |  | (385.7) | (475.2) | (419.4)
Deferred income taxes |  |  |  |  |  |  |  |  |  |  | 12.7 | 9.1 | 14.4
Loss on debt extinguishment |  |  |  |  |  |  |  |  |  |  | 38.4 | 0.0 | 0.0
Change in - |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable from related parties |  |  |  |  |  |  |  |  |  |  | 0.0 | 3.3 | (2.1)
Prepaid taxes |  |  |  |  |  |  |  |  |  |  | (7.9) | (46.5) | 17.5
Accounts payable to related parties |  |  |  |  |  |  |  |  |  |  | 29.2 | (5.2) | 4.6
Other current liabilities |  |  |  |  |  |  |  |  |  |  | (2.4) | 1.5 | 4.7
Other, net |  |  |  |  |  |  |  |  |  |  | 9.6 | 7.0 | 5.6
Net cash provided by operating activities |  |  |  |  |  |  |  |  |  |  | 893.8 | 628.0 | 684.6
Investing activities |  |  |  |  |  |  |  |  |  |  |  |  |
Capital contributions to subsidiaries |  |  |  |  |  |  |  |  |  |  | (1,026.1) | (602.3) | (448.7)
Return of capital from subsidiaries |  |  |  |  |  |  |  |  |  |  | 602.8 | 337.3 | 290.2
Short-term notes receivable from related parties, net |  |  |  |  |  |  |  |  |  |  | (88.3) | 48.5 | (6.9)
Issuance of long-term notes receivable from UMERC |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 | (100.0)
Redemption of long-term notes receivable from UMERC |  |  |  |  |  |  |  |  |  |  | 0.0 | 150.0 | 0.0
Other, net |  |  |  |  |  |  |  |  |  |  | 3.7 | (0.6) | 6.4
Net cash used in investing activities |  |  |  |  |  |  |  |  |  |  | (507.9) | (67.1) | (259.0)
Financing activities |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise of stock options |  |  |  |  |  |  |  |  |  |  | 43.8 | 67.0 | 29.1
Purchase of common stock |  |  |  |  |  |  |  |  |  |  | (99.2) | (140.1) | (72.4)
Dividends paid on common stock |  |  |  |  |  |  |  |  |  |  | (798.0) | (744.5) | (697.3)
Issuance of long-term debt |  |  |  |  |  |  |  |  |  |  | 1,650.0 | 350.0 | 600.0
Retirement of long-term debt |  |  |  |  |  |  |  |  |  |  | (1,430.0) | 0.0 | (300.0)
Issuance of short-term loan |  |  |  |  |  |  |  |  |  |  | 340.0 | 0.0 | 0.0
Change in other short-term debt |  |  |  |  |  |  |  |  |  |  | 145.7 | (213.7) | 53.6
Short-term notes payable to related parties, net |  |  |  |  |  |  |  |  |  |  | (186.3) | 90.4 | (6.2)
Payments for debt extinguishment and issuance costs |  |  |  |  |  |  |  |  |  |  | (47.3) | (0.8) | (1.2)
Other, net |  |  |  |  |  |  |  |  |  |  | (1.1) | (1.5) | (2.4)
Net cash used in financing activities |  |  |  |  |  |  |  |  |  |  | 382.4 | 593.2 | 396.8
Net change in cash and cash equivalents |  |  |  |  |  |  |  |  |  |  | 3.5 | (32.3) | 28.8
Cash and cash equivalents at beginning of year |  |  |  |  |  | $ 0.5 |  |  |  | $ 32.8 | 0.5 | 32.8 | 4.0
Cash and cash equivalents at end of year | $ 4.0 |  | $ 4.0 |  |  |  | $ 0.5 |  |  |  | $ 4.0 | $ 0.5 | $ 32.8

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