You can't get it until after 20 weeks, but then it says you have to give it to your employer by 25/26 weeks, which doesn't leave a whole lot of time LOL
My appointment was bang on 20 weeks so I asked for it (twice!) as my next appointment isn't til 28 weeks and your employer is supposed to have it by then.
I'm sending mine off this week as I need Mat allowance (don't earn enough to get SMP but only under by about £10 a week lol).
Filled in the Mat Allowance form but needed bank details so will fill that bit in tomorrow and get it posted. I'm wanting to take maternity leave as early as possible lol (29 weeks) haha.