compiles fine without errors.
I saw too many errors then would not compile without too many errors.

I fixed the reported errors until it compiled without any, but did not test your code.
Compare them and test.
Code:
'P16f88_Tx


INCLUDE "modedefs.bas"
DEFINE OSC 4
ansel = %00000000
Led var PORTB.4
BotonA Var  PORTB.1


high led
pause 500
low led


transmit:
if botona = 0 then Send_1
low led
goto transmit




Send_1:
high led
serout PORTB.0, T1200, ["A"]
goto transmit
End

'--------------------------------

'P16f88_Rx


INCLUDE "modedefs.bas"
DEFINE OSC 4
ansel = %00000000
leda VAR PORTB.1
RX_data var byte


high leda
pause 250
low leda




receive:
serin PORTB.0, T1200, [RX_data]
pause 500
if RX_data = "A" then one
low leda
goto receive


one:
high leda
goto receive
end