can be difficult, sometimes. Others may be able to offer better ideas, but some that have worked for me or were suggested to me to try are;
Use a plant that attracts them (catnip, i think) in a different part of the garden, away from lawn.
Sprinkle pepper on the area they use.
Spray repellents like cat-a-pult by Bayer.
My dog made the garden a no cat zone, until old age caught up with him.
Last idea, which sounds far fetchedand was suggested to me and i haven't tried yet, is to ask a zoo for some Big cat (tiger etc) droppings. The thought is that the local tabby sniffs and things that there is a bigger cat now claiming the patch and so will move on. What tabby would be brave enough to try and steal a tigers toilet.

Personally, I have that only found that physical barriers stop cats - so lots of stakes in the borders where they pee/poo.

Unlikely that cats are using your lawn, they bury their excrement. More likely to be a dog or a fox.

Some cats do use lawns, MG - I have a friend who's nearly driven mad by them. It tends to be the "boss cat" who does it, and the lesser cats are more likely to dig holes for their offerings, which can be just as annoying if they use a seed bed...

Thanks for your posts.

Hmm, in my experience, cats use lawns as toilets only when the grass is long - lazy un neutered toms might do it as well, but its not that common - it usually turns out to be foxes. If it is cats, keep the grass cut and short.

i do keep it short but the weather is unpredictable so cant be cut that day.

I realise you keep it cut from your other question, which I found after this one.

I still think it is more likely to be a fox or foxes this is their blatant way of warning off other animals

ive seen a ginger cat spraying on my patio also.

Whether its cats or foxes doesn't make a difference, really - the only effective method I've known is one put together by an electrical engineer friend of mine - he wired one of those PIR detector switches to his sprinkler, so every time there was movement in the garden, the sprinkler came on. Worked a treat, but not something I'd be capable of doing, don't know about you. Foxes seem less bothered by the sudden spray of water though.

sounds expensive but thanks anyway.

Ah yes all cats, male & female, spray - it is one way they communicate with each other. Scrub the area with Jayes Fluid.

very tricky. my two use the garden as a loo all the time. i am dreading planting everything out and laying my grass seed when its all ready! the grass will go under netting but the suggestion of putting twigs and things on the border is the best idea, OR make a small area of your garden away from the house nicely dug over with nothing in it and hope they use that bit!!!! if its all nicely dug they love it. once its settled and much firmer they go off it, unless they are very used to that area. the 'get off my lawn' stuff works but only for a very short time. i have never tried this myself but i may try it also, one of mine hates anything minty so i think i will sprinkly mint or essential oil around to see if that stops it. bizarly 15 years ago i actually got a cat because i was fed up with all the neighbourhood cats using the garden as a loo. i had heard that cats never use their own garden WRONG!!!! but i love mine to death now and a bit of poo and holes are worth it. feel sorry for people who dont have them though, most annoying!

Be careful with essential oils around cats, they are too strong and can actually make the cat ill.

yes you are right moon growe, but a sprinkle on the soil will be fine as it will evaporate quite quickly, i certainly wouldnt suggest pouring it all over! just a few drops. citronella may be ok, that is what the 'keep off my lawns' use i think. even humans should only use tea tree and lavender neat on skin let alone furry ones :-)

I have four cats, and not one is allowed to use the garden as a toilet...they use the field..There are however, two dirty little devils that live across the road and are too lazy to walk further than my outside front border...poo and do not cover it...I have a very handy water pistol...and they get squirted Ernie...same applies to any cat spraying...then afterwards I spray the affected area with my Garlic spray that I use for Aphids...see recipe on my Aphid Blog.... Ernie you can spray your Lawn with the Garlic Spray it wont harm your Lawn or Plants...Hope this helps...

Thanks very much. i will try this. im off on my hols soon so i bet they run riot. thanks anyway.