Convert datetime field to just a date field in SQL (Oracle)

Just use the function TRUNC.

SELECT DISTINCT
TRUNC(C.RECEIPTDATE),
(I.CLIENTID ||' - '||PO.CLIENTNAME) AS CLIENT,
D.INVOICEID,
TRUNC(D.SVCFROMDATE),
TRUNC(D.SVCTODATE),
D.SVCCODE
FROM M_EQP_ORDERS
WHERE.....

Use to_char function:

SELECT DISTINCT
to_char(C.RECEIPTDATE,'DD/MM/YYYY'),
(I.CLIENTID ||' - '||PO.CLIENTNAME) AS CLIENT,
D.INVOICEID,
D.SVCFROMDATE,
D.SVCTODATE,
D.SVCCODE
FROM M_EQP_ORDERS
WHERE.....

DEPENDS on the data type.

If the column is DATE data type, then, as suggested already, TRUNC would do the job to display. But, if your locale-specific NLS date settings are different, then you will still see the time portion as midnight.

Else, you need to use TO_DATE with proper FORMAT and apply TRUNC to it.

update

If you only want to display, use TO_CHAR, else, if you have a filter in your WHERE clause, then remember TO_CHAR doesn't return DATE, it converts it into literal.