MySQL 5.6

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
CREATE TABLE recurring_bills
    (`theUniqueId` int auto_increment primary key
     , `customerId` int
     , `chargeId` varchar(7)
     , `LastDay` date
     , `IsDeleted` int
)
;
    
INSERT INTO recurring_bills
    (`customerId`, `chargeId`, `LastDay`, `IsDeleted`)
VALUES
    (1, 'charge1', NULL, 0),
    (1, 'charge1', '2022-05-23', 0),
    (2, 'charge2', '2022-05-23', 0),
    (2, 'charge2', '2021-05-23', 0),
    (3, 'charge3', NULL, 1),
    (3, 'charge3', NULL, 0)
;
-- Show all duplicates
SELECT * 
FROM   recurring_bills dupe
WHERE dupe.IsDeleted = 0
AND ( dupe.LastDay > '2022-03-10' OR
      dupe.LastDay IS NULL 
    )
AND EXISTS (
    SELECT NULL
    FROM   recurring_bills b
    WHERE b.customerId = dupe.customerId
    AND   b.chargeId   = dupe.chargeId 
    AND   b.IsDeleted  = dupe.IsDeleted 
    AND   b.theUniqueId <> dupe.theUniqueId
    AND ( b.LastDay > '2022-03-10' OR 
          b.LastDay IS NULL 
        )
)   


theUniqueId
customerId
chargeId
LastDay
IsDeleted


1
1
charge1
null
0

2
1
charge1
2022-05-23
0


-- Show single record per dupe combination
SELECT * 
FROM   recurring_bills dupe
WHERE dupe.IsDeleted = 0
AND ( dupe.LastDay > '2022-03-10' OR
      dupe.LastDay IS NULL 
    )
AND EXISTS (
    SELECT NULL
    FROM   recurring_bills b
    WHERE b.customerId = dupe.customerId
    AND   b.chargeId   = dupe.chargeId 
    AND   b.IsDeleted  = dupe.IsDeleted 
    AND   b.theUniqueId <> dupe.theUniqueId
    AND ( b.LastDay > '2022-03-10' OR 
          b.LastDay IS NULL 
        )
)   
 
GROUP BY dupe.customerId, dupe.chargeId


theUniqueId
customerId
chargeId
LastDay
IsDeleted


1
1
charge1
null
0